A Very Different Earth™

What is the "Greenhouse Effect" and How Does It Work?

noreply@blogger.com (David) — Mon, 17 Sep 2012 17:19:00 +0000

This post will help you understand

Why the "greenhouse effect" has to do with gases in the atmosphere,
How these "greenhouse gases" in the atmosphere warm the Earth (and what that has to do with things that are "red hot"),
What this implies for future warming as we put more of these gases into the atmosphere.

The use of a toaster is not required, but it helps if you know how one works.

What Is The Greenhouse Effect?

The "greenhouse effect" refers to how gases in the atmosphere which absorb infrared radiation make the Earth warmer than it would be without them. (It has nothing to do with the way greenhouses work to protect plants by trapping warm air in an enclosure. That's just its name.)

There are two ways to understand this phenomenon:

Some gases in the atmosphere absorb infrared radiation emitted from the surface of the earth. This warms them up and they radiate energy, some of which heats the surface in turn.
Gases in the atmosphere that absorb infrared radiation from the surface make the atmosphere more opaque to that radiation, preventing transmission from the surface into space. (Radiation into space still happens, but from high in the atmosphere where it is colder and thus radiates less.)

Both of these ideas involve reduction in the flow of energy from the surface and lower atmosphere into space as radiation. The loss of radiation to space is less than it would have been if there were less of these "greenhouse gases". Since the flow of energy is reduced, the Earth is kept warmer.

Over time the Earth reaches a temperature that radiates away as much energy as it receives from the Sun. But when the amount of greenhouse gases in the atmosphere changes for some reason it takes time for the planet to warm or cool enough to restore that energy balance. That is why the "greenhouse effect" is in the news so much today--the concentrations of these greenhouse gases in the atmosphere are changing at unprecedented rates.

The Physics of the Greenhouse Effect

It is easy to understand the greenhouse effect if you comprehend these simple facts:

The Earth is a big warm rock
Warm things emit radiation
Other things absorb some of that radiation

In particular the "greenhouse gases" in the atmosphere strongly absorb the infrared radiation the Earth emits

When something absorbs radiation it heats up
Warm things emit radiation (2. again)
Other things absorb some of that radiation (3. again)

Some of the radiation from the atmosphere (see 5.) is absorbed by the Earth, which warms it (see 4.)
Some of the radiation from the atmosphere escapes into space, but less than if the atmosphere hadn't absorbed it on its way from the surface and sent some of it back down.

Let's look at that process in more detail:

1. The Earth is a big warm rock. The average surface temperature is about 14.5 degrees C (287.5 degrees K). This is the near-surface atmospheric temperature (as would be measured by a thermometer at a weather station) averaged the seasons, over day and night, and over the geography of the earth. (See Wikipedia article Instrumental temperature record.) The Earth is warmed by radiation from the Sun that it absorbs, and by its own internal heat, some left over from its formation and some from radioactive decay of elements it is made from.

2. Warm things emit radiation. Any object radiates heat, in the form of electromagnetic radiation. Everybody is familiar with the idea of an object being "red hot". An object that hot emits enough light that we can see it, mostly in the infrared part of the spectrum but some at long visible wavelengths. When an object is "white hot" it emits even more radiation, including a lot of visible light and a substantial amount of ultraviolet radiation.

2a. The warmer a thing is the more radiation it emits. This is known as the Stefan–Boltzmann law. (See Wikipedia article Thermal radiation.)

You can easily demonstrate this. If you hold your hand near a toaster (not in a toaster!), where the radiation from the toaster's coils can hit it, the radiation from the toasters coils will be absorbed by your hand. Your skin will be warmed by this radiation, and the more radiation there is the more it will be warmed.

When the toaster is off and the coils are at room temperature you won't feel the warming of your skin. The nerves in your skin don't do much when they are just at room temperature.

(Everything that is not at a temperature of absolute zero emits radiation. But hotter things emit a lot more radiation than colder things. Notice that the Stefan-Boltzmann law says that the amount of energy radiated is proportional to the fourth power of the temperature: j*=εσT⁴. So coils glowing red hot--about 1,000 K--are hotter than coils at room temperature of about 293 K, about 700 degrees Kelvin hotter. They are three times as hot, but they emit more than 100 times as much radiation.)

But when the toaster is on, and the coils are glowing red hot, they will emit a lot of infrared radiation (and a little visible radiation). Your hand would be warmed noticeably as it absorbed this greater quantity of radiation.

At 287.5 degrees Kelvin (14.5 degrees Celsius) most of the radiation the Earth emits is infrared radiation. None of it is in the visible range. (Even at 45 degrees Celsius, a really hot day, none none of the Earth's radiation is in the visible range. This is why the Earth does not appear to glow on a really hot night.)

3. The atmosphere absorbs radiation. Molecules of the gases that make up our atmosphere absorb radiation. Obviously the atmosphere doesn't absorb all wavelengths of radiation equally. It doesn't absorb much in the range of visible light (it is transparent to visible light). This is why we can see the Sun, Moon and stars. The oxygen and ozone in the atmosphere absorb a lot of ultraviolet radiation coming from the Sun. That is why organisms can live on the surface of the Earth (UV kills microorganisms and causes skin cancer in people, for example).

The atmosphere is mostly oxygen and nitrogen, but it is about 0.035% carbon dioxide. Carbon dioxide absorbs infrared radiation very strongly. Since the warm Earth emits mostly infrared radiation (with a peak at wavelengths of about 10^-5 meters) and CO₂ absorbs infrared radiation (especially that with a wavelength longer than about 1.3x10^-5 meters) you can see that a lot of the infrared radiation from the surface of the Earth is absorbed by CO₂ in the atmosphere. (The situation is similar for other "greenhouse gases" such as CFCs, nitrous oxide, methane and water vapor.) (See Greenhouse Gas Absorption Spectrum.)

4. When something absorbs radiation it heats up. The photons of radiation can interact with matter. How they interact depends on the properties of the photon (wavelength) and the properties of the atom or molecule of matter. (At the wavelengths we are talking about these properties mainly have to do with the energy states of its electrons.) When substances absorb radiative energy they increase their thermal energy. They get warmer.

2. again: Warm things emit radiation (see above). The warmer they are the more radiation they emit. The warmed greenhouse gases emit more infrared radiation than they did when it was cooler (see 2a. above). Some of that radiation escapes into space. Some is absorbed by other parts of the atmosphere. And some if it is absorbed by the Earth below, making it a little warmer (see 4. above).

So that's how the "greenhouse effect" works:

Radiation from the Sun warms the Earth and the atmosphere
The Earth emits infrared radiation (the warmer it is the more it emits)
The "greenhouse gases" in the atmosphere, especially CO₂, absorb some of that radiation from the earth, and this warms them up (the more of these gases there are the more they absorb)
The warm gases in the atmosphere emit infrared radiation (and the warmer they are, and the more of them there are, the more they emit)
Some of the infrared radiation from the "greenhouse gases" in the atmosphere is absorbed by the Earth, warming it a little more
Loop back and repeat

So it doesn't work at all like a greenhouse. (Not that most people have much idea how greenhouses, also called glasshouses, work, or even what they are.) It isn't a result of the atmosphere "insulating" the Earth, like a blanket. It has to do with the gases in the atmosphere absorbing radiation, heating up, and warming the Earth below by their own radiation. But the names "greenhouse effect" and "greenhouse gases" are well established, so we might as well go ahead and use them.

The Net Result

The diagram below shows how all this works in terms of the Earth's energy balance.

As you can see, the net imbalance (energy in minus energy out) is only 0.9 Watts per square meter. (Other estimates give net forcing of approximately 1 to 3 Watts per square meter.) Whatever the actual figure, it is enough to warm the Earth significantly over time.

Consequences

Also note that the net absorbed is only 0.26% of the total incoming energy flux. It only takes a small change in the transparency of the atmosphere in the infrared to change the outgoing long-wave (infrared) radiation enough to affect the surface temperature. And of course the more greenhouse gases in the atmosphere, the greater the climate forcing.

How much will the Earth's temperature rise because of this 1 or 2 Watt per square meter forcing? That is the subject of urgent research. Current thinking is that the level of greenhouse gas in the atmosphere today, if we didn't put any more up there, might lead to a further increase in global temperature of one or two degrees Celsius or so.

But there are many difficulties with this estimate:

Feedback effects. As the Earth warms up there will be changes in the global energy balance that might make it warm faster or slower, such as

Melting of ice. Ice is highly reflective, so if it melts to expose bare ground or open sea less incoming solar radiation will be reflected back to space ("Reflected by Surface" in the diagram above).
Vaporization of methane in permafrost and undersea deposits. Methane is one of the most significant greenhouse gases, and there are vast amounts of it tied up in frozen permafrost or in deposits of methane hydrates on the sea floor. If warming of the sea causes melting and release of some methane hydrates this could vastly decrease the transparency of the atmosphere to long-wave radiation, keeping more heat on the Earth. It is thought that when this happened in the geologic past it led to an earth many degrees hotter than today's.
Warming seas. Cold water can absorb more carbon dioxide than warmer water. So as that 1 Watt per square meter radiative forcing warms the oceans, more carbon dioxide will be left in the atmosphere to act as a greenhouse gas.
Clouds. As the climate warms the weather will change. There might be more clouds, or less, or their distribution might change. Clouds are an important part of the "Reflected by Clouds and Atmosphere" component of the energy budget in the diagram.
Water vapor. Warmer air can hold more water vapor, and water vapor is a significant greenhouse gas.

Continued emissions.

We have already perturbed the planet's energy balance by putting around a trillion tonnes of greenhouse gases into the atmosphere over the past couple of centuries by burning fossil fuels and by land-use changes (burning forests). That is why the energy budget is out of balance by one or two Watts per square meter. But we continue to put about 35 billion additional tonnes of greenhouse gases into the air every year. And that annual emission figure continues to increase. So the concentration in the atmosphere will increase, the transparency of the atmosphere to infrared radiation will decrease, and the greenhouse climate forcing will increase. We are on course to put at least another trillion tonnes of greenhouse gases into the atmosphere by 2050, probably closer to two trillion.

I hope you can see why putting more CO₂ into the atmosphere, more than the land and the seas can reabsorb, could make the atmosphere, and thus the Earth, warmer, perhaps much warmer.

Get ready for A Very Different Earth.

The toaster image is from Explain that Stuff published under a Creative Commons License.

The energy balance diagram is from this UK government site, and is protected by Crown copyright. Used by permission.

Here is another explanation of the greenhouse effect.

This post is shared from Science In Action.

Rapid Change in the Arctic

noreply@blogger.com (David) — Tue, 10 May 2011 15:05:00 +0000

The Arctic Monitoring and Assessment Program (AMAP) has issued its latest Snow, Water, Ice and Permafrost in the Arctic report (SWIPA), with recent data on changes in the arctic and how they will affect us all.

The major finding is that changes the Arctic is changing faster than previously projected. The report calls attention to the social and economic implications of these changes. But most of us don't live in the Arctic, so why should we care what happens up there?

Sea Level

Many news reports (see two examples below) have focused on the statement that sea levels will rise up to 1.6 meters above 1990 levels by 2100. This is not strictly a finding of the SWIPA study. In fact it just quotes other model results, saying:

High uncertainty surrounds estimates of future global sea level. Latest models predict a rise of 0.9 to 1.6 m above the 1990 level by 2100, with Arctic ice making a significant contribution.

SWIPA itself doesn't say why this warming is happening, but agrees with the IPCC:

In attributing the cause of warming in the Arctic, SWIPA refers to the findings of the Fourth Assessment Report from the Intergovernmental Panel on Climate Change (IPCC). This states that "Most of the observed increase in global average temperatures since the mid-20th century is very likely [> 90% probability] due to the observed increase in anthropogenic GHG [greenhouse gas] concentrations".

It does conclude, however, that "melting glaciers and ice sheets worldwide have become the biggest contributor to global sea level rise," and that "These contributions from the Arctic to global sea level rise are much greater than previously measured."

Key Findings

The English executive summary is in PDF here. The key findings it lists are:

"The past six years (2005–2010) have been the warmest period ever recorded in the Arctic."
"Snow and sea ice are interacting with the climate system to accelerate warming" (positive feedbacks--see finding 12 below).
"The extent and duration of snow cover and sea ice have decreased across the Arctic. Temperatures in the permafrost have risen by up to 2 °C. The southern limit of permafrost has moved northward in Russia and Canada."
"Multiyear sea ice, mountain glaciers, ice caps and the Greenland Ice Sheet have all been declining faster since 2000 than they did in the previous decade."
"Model projections reported by the Intergovernmental Panel on Climate Change (IPCC) in 2007 underestimated the rates of change now observed in sea ice."
"Average snow cover duration is projected to decline by up to 20% by 2050."
"The Arctic Ocean is projected to become nearly ice-free in summer within this century, likely within the next thirty to forty years."
These and other changes are altering "the characteristics of Arctic ecosystems and in some cases loss of entire habitats. This has consequences for people who receive benefits from Arctic ecosystems."
"The observed and expected future changes to the Arctic cryosphere impact Arctic society on many levels," creating both threats and opportunities.
"Transport options and access to resources are radically changed by differences in the distribution and seasonal occurrence of snow, water, ice and permafrost."
"Arctic infrastructure faces increased risks of damage."
"Loss of ice and snow in the Arctic enhances climate warming by increasing absorption of the sun’s energy at the surface of the planet. It could also dramatically increase emissions of carbon dioxide and methane and change large-scale ocean currents."
"Arctic glaciers, ice caps and the Greenland Ice Sheet contributed over 40% of the global sea level rise of around 3 mm per year observed between 2003 and 2008. In the future, global sea level is projected to rise by 0.9–1.6 m by 2100 and Arctic ice loss will make a substantial contribution to this."
"Everyone who lives, works or does business in the Arctic will need to adapt to changes in the cryosphere", and this will require significant investment.
Considerable uncertainty remains and more research is needed. (The traditional coda to any scientific report.)

About AMAP

The Arctic Monitoring and Assessment Programme is a leading, authoritative, scientific program to understand what is going on in the arctic:

AMAP is an international organization established in 1991 to implement components of the Arctic Environmental Protection Strategy (AEPS).

Now a programme group of the Arctic Council, AMAP's current objective is "providing reliable and sufficient information on the status of, and threats to, the Arctic environment, and providing scientific advice on actions to be taken in order to support Arctic governments in their efforts to take remedial and preventive actions relating to contaminants".

So its findings carry considerable weight.

Reuters story

Huffington Post story

Is "Dangerous Interference" Inevitable?

noreply@blogger.com (David) — Tue, 05 Oct 2010 22:16:00 +0000

Should We Just Throw In The Towel?

The Stern Review warned that adapting to climate change would be significantly more expensive than avoiding it in the first place (see this earlier post). But the opportunity to slow or reduce ("mitigate") climate change may have been lost. It may already be too late. Now we have to start facing the costs of adaptation to inevitable changes.

At least that is the gist of a recent report by a British expert committee, and accompanying comments by the UK's new environment secretary.

And other evidence, from scientific research and from China's continued rapid economic growth, with corresponding increases in energy consumption, suggests that we will substantially overshoot the proposed target of 2°C warming above pre-industrial levels.

Yet more research suggests that the 2°C target was in the danger zone anyway.

So here is the information summarized in this post:

China's growth takes us past targets
2°C target was too low
We can't stay below 2°C anyway
UK Environment Minister: Change inevitable

Soaring Chinese Growth

A recent article in Reuters noted that the International Energy Agency suggested that China's greenhouse gas emissions could rise to a peak of about 8.4 billion tonnes of CO2 per year by around 2020 and then begin to decline. Such a scenario would still allow global warming to be kept below about 2°C above pre-industrial levels--a supposedly "safe" level.

But the Netherlands Environmental Assessment Agency in their report "No growth in total global CO₂ emissions in 2009" estimate that China's emissions from fuel burning reached 8.1 billion tonnes of CO₂ in 2009, and India's reached 1.7 billion tonnes. (Press release here, PDF of report here.) China's emissions rose at 9% and India's at 6%. At that rate China will easily exceed 8.4 billion tonnes of emissions by 2010 or 2011.

The almost-global recession caused emissions to drop in developed economies, but increases in developing economies largely canceled out such reductions.

(Note that "The assessment excludes CO₂ emissions from deforestation and logging, forest and peat fires, from post-burn decay of remaining above-ground biomass, and from decomposition of organic carbon in drained peat soils. The latter mostly affects developing countries. These sources could add as much as a further 20% to global CO₂ emissions." Source)

Even with proposed "efficiency gains, China's expected rapid economic growth will push its absolute volume of emissions to between 9.6 and 10.1 billion tonnes of CO₂ per year by 2020, compared with 5.2 billion tonnes in 2005, according to a study from the Chinese Academy of Sciences," said Reuters.

Keeping Warming Below 2°C Won't Save Us

A lot of international discussion, and the Copenhagen Accord, mention the idea that if we can keep global warming below 2°C above pre-industrial levels we will avoid "dangerous anthropogenic interference with the climate system". This target now seems dubious. Maybe it should be 1.5°C or even lower.

Chris S.M. Turney and Richard T. Jones of the University of Exeter have published "Does the Agulhas Current amplify global temperatures during super-interglacials?" in the Journal of Quaternary Science (full text here). They looked at climate during the Last Interglacial, spanning the period from about 130 to 116 thousand years ago, when sea level was 6.6–9.4 meters higher than today. The question was, what was the global temperature then? And, what were the mechanisms of regional distribution of that warming?

With the usual caveats, "Our results suggest the world was 1.5 ± 0.1°C warmer than the period AD 1961–1990". (The underlying drivers of warming at that time were changes in the amount of energy reaching the Earth from the Sun, due to variations in the Earth's orbit, and resulting changes in the carbon cycle.) They believe that warming in the southern hemisphere altered prevailing winds and thus ocean currents, allowing more upwelling of carbon-rich deep waters thus amplifying warming in the northern hemisphere.

The authors note that similar changes in southern-hemisphere winds and ocean currents seem to be happening today, and that similar feedbacks driving more warming may occur.

They go on to say, "if our estimate of global temperatures during the LIG is broadly correct and was higher than pre-industrial levels by ∼1.9°C, this leads us to question whether a 2°C target for stabilising global temperatures should be considered ‘safe’", since sea levels were so much higher back then at those temperatures.

Many others have raised similar concerns. See this review of James Hansen's book.

We're Going to Overshoot 2°C Anyway

A recent paper by Rogelj et al. in Environmental Research Letters, "Analysis of the Copenhagen Accord pledges and its global climatic impacts—a snapshot of dissonant ambitions", points out that if you total up the emission-reduction "pledges" made in the Copenhagen Accord the resulting rates of continuing emissions are very likely to take us past 2°C of warming. They find, regarding the developed countries:

Ultimately, even the optimistic interpretation of the Accord's pledges results in effective reductions by 2020 far outside the 25–40% range of aggregated emission reductions for developed countries specified in Box 13.7 of IPCC AR4. That box provided data for the lowest category of analysed mitigation scenarios which stabilize atmospheric CO₂eq concentrations between 445 and 490 ppm CO₂eq and have a best estimate global temperature increase of 2.0–2.4 °C at equilibrium.

Taking the countries at their word, the authors estimate global annual emissions of around 50 Gigatonnes CO₂ equivalent in 2020, up from about 39 GtCO₂eq in 1990 and 49 GtCO₂eq in 2004. They estimate that global emissions would reach 55 GtCO₂eq by 2050. To keep us under 2°C warming the estimated emissions in 2050 would have to be closer to 17 GtCO₂eq. They figure that "Case 1 with reference growth after 2020 results in a likely global temperature increase of 2.5–4.2 °C above pre-industrial in 2100 and is still increasing afterwards."

Thus even if the various countries deliver on their pledges to decrease (or, in some cases, increase) their emissions those emissions are likely going to take us above 490 ppm and above 2°C. (The conclusion of the paper is too depressing to quote, but I include it in a footnote.)

The UK Sees "Unavoidable" Climate Change

The Adaptation Subcommittee of the UK Committee on Climate Change has issued a report "How well prepared is the UK for climate change?". The report says that because of current and projected future climate change, the UK should be thinking about what its inhabitants, companies and institutions should be doing to deal with the impacts of that change.

Preparing for climate change today will reduce the costs and damages of a changing climate and allow UK businesses, the public sector, the third sector and individuals to take advantage of potential opportunities. Early action will help make the UK better prepared for today’s climate and ensure that decisions made today that have long-lasting consequences do not close off options and make it harder to adapt in the future.

They go on to make various specific recommendations. Access the Adaptation Subcommittee's report here. (About the committee.)

But the really interesting development was a speech given by new UK Environment Secretary Caroline Spelman on the occasion of the report's launch. She said:

Today’s report provides a wake-up call. It recognises that there is no part of our society which is immune from the effects of climate change. Which means that every part of our society must think about its resilience. ... This Government will not give up the battle to tackle the causes of climate change. ... But while it is vital that we continue the task of drastically cutting our greenhouse gas emissions, we know that we are already facing levels of unavoidable climate change. ... And UK climate change projections suggest even higher temperatures and more severe weather in the coming years. ... If more than 75% of our businesses remain unprotected we are in danger of ending up with a two-tier commercial sector - those that have adapted successfully and those who didn’t see it coming. ... What Government can do is provide them with information and models to help them calculate the risks. ... And the transition to a low carbon, well-adapted global economy could create hundreds of thousands of sustainable ‘green’ jobs.

(PDF of the speech here. Article about the speech in The Telegraph here.)

That sounds to me like a change in emphasis. "Low carbon" efforts will not be enough. Everybody has to start thinking, and acting, to protect themselves from the negative impacts of inevitable climate change. (There is particular emphasis on getting companies and local authorities to analyze their risks and address them, using tools (but not necessarily money) provided by the government.

Get ready for a very different earth.

Graph from Netherlands Environmental Assessment Agency, June 2010, No growth in total global CO2 emissions in 2009 (pdf here) by permission.

The Chris S.M. Turney and Richard T. Jones paper is Copyright © 2010 John Wiley & Sons, Ltd. Quotations used under fair use standards.

The Rogelj et al. is © IOP Publishing 2010. Quoted under fair use standards.

Conclusion of Rogelj et al. paper:

If the average national ambition level for 2020 is not substantially improved and loopholes closed in the continued negotiations, only low probability options remain for reaching the 2 °C (and possible 1.5 °C) ambition of the Accord. Most developed country submissions to the Accord indicate that only with a global and comprehensive agreement countries are inclined to commit to more, and likewise for developing countries the required level of support through financing, technology and capacity building is needed. With the negotiation mandates having been extended to the end of 2010, committing to higher ambitions and agreement by all Parties still remains possible. It is clear from this analysis that higher ambitions for 2020 are necessary to keep the options for 2 and 1.5 °C open without relying on potentially infeasible reduction rates after 2020. In addition, the absence of a mid-century emission goal—towards which Parties as a whole can work and which can serve as a yardstick of whether interim reductions by 2020 and 2030 are on the right track—is a critical deficit in the overall ambition level of the Copenhagen Accord.

Geoengineering Today

noreply@blogger.com (David) — Wed, 29 Sep 2010 17:54:00 +0000

Geoengineering . . . You're Looking At It

[crossposted from Doc's Green Blog]

"Geoengineering" refers to large-scale efforts to manipulate the climate. There are several current and recent activities that have been undertaken for other purposes, but which have the effect of changing climate, for good or ill.

We will set aside the deliberate release of 25 billion tonnes of greenhouse gases from combustion of fossil fuels each year, a geoengineering "experiment" that seems already to be creating many interesting effects. Although this is one of the largest geoengineering projects ever undertaken, it has been discussed in some detail elsewhere.

The three current geoengineering programs this post will consider are:

China's "Great Green Wall"
Large-scale expansion of irrigation
Large-scale deforestation

Afforestation Changes The Climate

Since 1978 China has been engaged in a vast project that has been called the "Great Green Wall". In 1981 the National People’s Congress passed a resolution to require every citizen above age 11 to plant at least three Poplar, Eucalyptus, Larch or other saplings every year. [Source] Afforestation has already covered 500,000 square kilometres with new artificial forest, and China hopes to have such forests on 400 million hectares--more than 42% of its land area--by 2050.

Chinese Vice Premier Hui Liangyu recently called for even greater efforts to increase China's forest cover.

The immediate goal of this program is to slow the encroachment of desert from the north and west into areas formerly grassland. Whether artificial forests can do this remains to be seen. And there are some concerns about other effects, such as increased water use. [More at Wikipedia.] A similar effort was the shelterbelt program in the U.S. Great Plains in the 1930s, but that was not on a Chinese scale.

Since forests affect the water cycle, albedo, and cloud cover of an area they can be expected to modify the local climate, and perhaps the climate downwind.

Irrigation Changes The Climate

Large programs of crop irrigation in Asia and North America result in large quantities of water evaporating from fields and water channels, and by transpiration through plants.

Because of the latent heat of water, more evaporation means more cooling in some places, and more rain means more warming in other places. (What is latent heat? See this post at Science In Action.) A recent article in the Journal of Geophysical Research (pdf here, New York Times Green blog post about it here) says irrigation may be causing cooling in some regions, locally masking the effects of global warming.

The model runs reported in this paper suggest that parts of northern India may have experienced several degrees of cooling due to all the heat absorbed by irrigation water applied to crops in the later part of the 20th century. Weather patterns may even have been affected enough to reduce the amount of rain in the Bay of Bengal branch of the Southwest Monsoon. (Other researchers got somewhat different or even contradictory results with different models.)

This is a bit scary because if groundwater depletion leads to reduction in irrigation in the future, the resulting reduction of cooling effect could have both local an regional climate effects, including sharply higher temperatures and changes in rainfall amounts and distribution.

Deforestation Changes The Climate

Large-scale deforestation for conversion of forest to pasture or cropland is an old story. Such deforestation took place over much of Europe and temperate North America in earlier centuries. A similar massive land-use change was the breaking up of the American prairie grasslands for farming in the 19th century.

When forests are burned (the usual method) to clear them for agriculture the carbon trapped in the trees is dumped into the atmosphere. Soot and other particulates are also released in great quantities. Both CO2 and black carbon have significant local and global effects on climate.

The Nature Conservancy says "deforestation and land use change contributes approximately 20 to 25 percent of the carbon emissions that cause climate change." This Wikipedia article on per-capita greenhouse gas emissions by country, which uses data from the World Resources Institute for 2000, suggests land-use changes account for about 17% of greenhouse gas emissions.

So land-use changes, mostly deforestation, annually release about the same amount of greenhouse gases as the USA or China does from all burning of fossil fuels.

The Future of Geoengineering

Several enormous geoengineering projects have been discussed as ways to undo some of the damage the earlier geoengineering projects mentioned above are causing. This previous post looks at some of the limitations and potential impacts of such schemes. Whether such consequences are "unintended", "unavoidable", or "somebody else's problem" will be part of the discussion of these projects in years to come.

Storms of My Grandchildren--James Hansen

noreply@blogger.com (David) — Tue, 14 Sep 2010 02:10:00 +0000

Serious Science for Critical Times

[Crossposted from Doc's Green Blog.]

Dr. James Hansen has written a personal, idiosyncratic, urgent, heartfelt book about climate change, past and future. The reader can feel his frustration at the stubborn inaction of governments in the face of what he sees as a looming disaster. But one also feels the warmth, the grandfatherliness, advertised by the book's title. Storms of My Grandchildren: The Truth About the Coming Climate Catastrophe and Our Last Chance to Save Humanity is more than half science, but it is part emotion. Scientists are people too.

The book's message in brief: It's worse than we thought, and here's why. Politicians are subservient to fossil fuel polluters. We have to do something about it unless we want to leave our descendants a severely damaged, and perhaps uninhabitable, world.

Hansen, in spite of the public role he has felt called upon to play, is 100% scientist. The book's structure uses his own journey as a researcher, and as an expert called upon to brief government leaders, to explain a lot of serious science. Climate forcings, paleoclimatology, aerosols, and more are presented to the reader in more depth than is usual for a book targeted at the general public.

Science of Climate Change

Color version of book's Figure 18
"Deep ocean temperature during the Cenozoic era"
[Do we really want to go back to the
Permian-Eocene Thermal Maximum
when sea levels were 75 meters higher?]

Some readers will be tempted to skip over some of the technical background. They will miss a fascinating part of the message. The scientific explanations are clear enough, although Dr. Hansen does take some shortcuts and requires the reader to pay attention. He has been immersed in this field for nearly 50 years and is used to its jargon, units and arguments. On the other hand this is not meant to be a textbook. Some compression and ellipsis is unavoidable. Readers who glide over the technical parts will be missing something important.

The science, Hansen is saying, is fundamental, undeniable, and convincing. He naturally feels that the reader should understand it in order to follow the argument that climate change is a serious threat to society. We may be setting in motion changes in the Earth's climate that could wipe out life on the planet and will certainly make life tougher for coming generations in this century. He urgently wants to get that message across.

Frustration with Inaction

This is a polemic. Hansen feels that politicians are in the palm of economic interests that benefit from continuing "business as usual" even in the face of urgent warnings of enormous risks. He is urging the people to take action.

His deep understanding of climate forcings and their effects in the past leads him to a much greater degree of alarm than many other scientists or environmentalists feel comfortable expressing. He has been criticized by other climate activists for lacking "a realistic idea of what is politically possible".

Hansen doesn't pull his punches. He thinks "cap and trade" is useless. He thinks expanded use of nuclear power is part of the solution. In these areas he treads beyond the strict boundaries of his expertise.

But when he says that targets like 450ppm of CO₂ in the atmosphere are much too high and will lead to disaster, he speaks of science he has studied in depth. He implores us to get back to 350ppm.

A striking conclusion from this analysis is the value of carbon dioxide--only 450 ppm, with estimated uncertainty of 100 ppm--at which the transition occurs from no large ice sheets to a glaciated Antarctica. This has a clear, strong implication for what constitutes a dangerous level of atmospheric carbon dioxide. If humanity burns most of the fossil fuels, doubling or tripling the preindustrial carbon dioxide level, Earth will surely head toward the ice-free condition, with sea level 75 meters (250 feet) higher than today. It is difficult to say how long it will take for the melting to be complete, but once ice sheet disintegration gets well under way, it will be impossible to stop.

With carbon dioxide the dominant climate forcing, as it is today, it obviously would be exceedingly foolish and dangerous to allow carbon dioxide to approach 450 ppm. [p. 160]

Neither politicians nor political climate activists and thought leaders like to be told that they are being "exceedingly foolish". Yet Hansen goes further. "But maybe Congress doesn't really care about your grandchildren. [p. 215]" "The present situation is analogous to that faced by Lincoln with slavery and Churchill with Nazism--the time for compromises and appeasement is over. [p. 211]"

A Book Worth Reading

Sophie and Connor,
Dr. Hansen's grandchildren

Dr. Hansen has decided that he knows something important, and that he must speak out about it. Not everyone will agree with the urgent, even intolerant, tone of his call to action. But it is based on true feelings founded on decades of serious science.

How the book's call to action affects you will depend on your biases and personality. Some will be moved to do something, some will be more informed but still passive, some will be annoyed, some will be indifferent. But all will have learned something.

The science that is at the heart of the book is worth seriously considering. If Hansen is right, our children, grandchildren and more distant heirs are going to curse us. We heard the message, and we are doing little or nothing. We blunder past tipping points with little concern for those who will have to live in the world we are leaving them.

Want to buy it? Click here: Storms of My Grandchildren: The Truth About the Coming Climate Catastrophe and Our Last Chance to Save Humanity

Dr. Hansen's web site is here.

He and Dr. Makiko Sato have also created the Updating the Climate Science page to supplement and update the content of Storms of my Grandchildren.

The book's official web page is here.

Good reviews of the book at Daily Kos and the Los Angeles Times.

The color version of the book's Figure 18 is from this site.

The picture of Sophie and Connor is from here. A black-and-white version is in the book at page 272.

The contents of the book are copyright © 2009 by James Hansen. The illustrations are copyright © 2009 by Mikiko Sato.

Geoengineering No Simple Solution

noreply@blogger.com (David) — Tue, 07 Sep 2010 18:20:00 +0000

Can we use geoengineering to avoid the worst effects of climate change caused by increasing atmospheric carbon dioxide? Don't count on it, say two recent scientific articles.

Sea Level Rise Can't Be Halted By Geoengineering

Researchers from China/Finland, the UK and Denmark modeled the effect of various geoengineering ideas on sea level rise. Their paper "Efficacy of geoengineering to limit 21st century sea-level rise" appears in the Proceedings of the National Academy of Sciences (abstract and access here). (They deserve thanks for making their paper open access.)

They find "sea-level rise by 2100 will likely be 30 cm higher than 2000 levels despite all but the most aggressive geoengineering under all except the most stringent greenhouse gas emissions scenarios." This means that even if we spend trillions on vast projects, and even if those projects work as planned, unless we also adopt tough measures to cut emissions sea level still goes up a foot.

And they say "Loss of low-lying land, combined with asset exposure to urban flooding due to the combined effects of climate change (sea-level rise and increased storminess), may reach 10% of projected global gross world product (GWP) in the 2070’s."

There are two things to consider when digesting that statement:

The authors are only talking about a meter of sea level rise in this century, at the lower end of current projections, and
The current recession cut the global economy by less than 2% from what it might have been without the recession. Imagine 10%.

They modeled several proposed projects:

Giant mirrors in space--These reduce climate forcing from the Sun's radiation, but leave greenhouse gases in the atmosphere where they continue to have their other negative effects such as ocean acidification. Also this project would be enormously expensive.

Who could think that launching 20 million tonnes of mirrors into space could be less of a blow to the economy than cutting greenhouse gas emissions by reducing coal use?
For comparison, the International Space Station weighs only 370,000 tonnes, and it has taken a decade to get it up there. It is the most expensive object ever constructed. It has been estimated to cost €100 billion over its 30-year life. Could taxpayers afford €5 trillion?

Aggressive afforestation, replanting cut forests and planting trees to create new forests, might be able to take some CO₂ out of the atmosphere, reducing that climate forcing. But CO₂ could only be reduced by about 45ppm. Humans have put more than a hundred ppm of CO₂ into the atmosphere over the past century or so, and are adding about 2ppm per year. So models still showed significant sea level rise.
Increasing biochar levels in the soil would reduce the CO₂ levels by even less--about 35ppm.
Aggressive conversion from petroleum and coal to biofuels with capture and storage of the resulting CO₂ from their combustion could reduce atmospheric CO₂ 180ppm by 2100.
A combination of afforestation, biochar sequestration and biofuels with carbon capture and storage could take 250ppm of CO₂ out of the atmosphere and might keep sea level rise to "only" 20 to 40 cm.
Injecting SO₂ into the atmosphere, equivalent to a major volcanic eruption every year and a half, could reduce global temperature rise a degree or so, but would leave the CO₂ in the atmosphere. Such a project might reduce sea level rise by 20cm or so. And if the program were ever ended warming would bounce back in a short time, with accompanying sea level rise.

And see the other findings below for more problems with SO₂ injection.

In the end they conclude "Substituting geoengineering for greenhouse gas emission abatement or removal constitutes a conscious risk transfer to future generations."

Geoengineering Helps Some But Hurts Others

Researchers from Carnegie Mellon and Oxford studied the regional impacts of various geoengineering concepts. Their work is reported in Nature Geoscience. (Abstract only here. Unfortunately these researchers did not make their findings open access.)

They modeled solar-radiation management by adding reflecting aerosols to the stratosphere. Previous modeling studies suggested that such an approach could stabilize global temperatures and reduce global precipitation. Their findings:

Our results confirm that solar-radiation management would generally lead to less extreme temperature and precipitation anomalies, compared with unmitigated greenhouse gas emissions. However, they also illustrate that it is physically not feasible to stabilize global precipitation and temperature simultaneously as long as atmospheric greenhouse gas concentrations continue to rise. Over time, simulated temperature and precipitation in large regions such as China and India vary significantly with different trajectories for solar-radiation management, and they diverge from historical baselines in different directions. Hence, it may not be possible to stabilize the climate in all regions simultaneously using solar-radiation management. Regional diversity in the response to different levels of solar-radiation management could make consensus about the optimal level of geoengineering difficult, if not impossible, to achieve.

So shooting millions of tonnes of SO2 into the stratosphere can cool the globe, but its effects are uneven. An article in The Economist provides more details:

A particularly salient example of this comes from Asia. There were a number of geoengineering scenarios in which the climate in both India and China in the 2020s looked quite like that of the 1990s, though in all geoengineering scenarios using this particular model India gets a bit wetter than it was before and in most of them China gets a bit drier. Go out to the 2070s, though, and the geoengineering scenarios strong enough to keep China’s temperature 1990s-ish cool India below its baseline temperature, while weaker scenarios that keep India’s temperature at the levels of the 1990s see China heat up.
That said, in both cases all the geoengineering options gave results for both temperature and precipitation closer to 1990s levels than the models projected for a world without geoengineering. In this sense both countries were "winners"—but maximising the benefits for one would still come at the expense of the other. The same lesson seems to apply quite generally across the world. Few if any regions stand out as certain losers from geoengineering if you accept that it is worth trading off a large change in temperature for a smaller drop in precipitation (in terms of change on the levels seen before the geoengineering). But different levels of geoengineering seem optimal for different regions.

So the question would be, who gets to decide what geoengineering to do? Presumably those who pay for it will control which projects get done. And naturally they will undertake projects that benefit themselves, even if they cause harm elsewhere in the world. This would be geopolitically very unfriendly, sort of like declaring war.

If these results hold I doubt we will see much geoengineering until and unless climate change gets so disruptive that the community of nations falls apart and its every one for itself.

A Scientific American blog post also covered the sea level rise story.

Plants Unhappy About Global Warming

noreply@blogger.com (David) — Thu, 02 Sep 2010 20:55:00 +0000

Rice field in Bangladesh

New science raises serious concerns about the negative impact of global warming on crop yields and plant productivity in general.

This could be one of the most severe social and economic effects of climate change.

Rice Yields Hurt By Warming

Researchers from the University of California, Duke, National Bureau of Economic Research, IRRI and FAO published a very revealing paper in PNAS. They studied 227 intensively managed irrigated rice farms in six important rice-producing countries over several years. Their findings "imply a net negative impact on yield from moderate warming in coming decades. Beyond that, the impact would likely become more negative, because prior research indicates that the impact of maximum temperature becomes negative at higher levels." Rising temperatures, especially nighttime temperatures, will hurt rice yields.

The paper is behind a pay wall, but there is a good BBC News article on their results. It says they "found that over the last 25 years, the growth in yields has fallen by 10-20% in some locations, as night-time temperatures have risen. ... Although yields have risen as farming methods improved, the rate of growth has slowed as nights have grown warmer." And "if temperatures continue to rise as computer models of climate project, Mr Welch says hotter days will eventually begin to bring yields down."

The question is whether rice improvement efforts (plant breeding) can get ahead of the negative effects of rising temperatures.

This EurekAlert release summarizes the results.

Net Plant Primary Production Down

Researchers at the University of Montana studied terrestrial net primary production. Net primary production (NPP) is the total net fixation of carbon by photosynthesis in an ecosystem. They found that "Large-scale droughts have reduced regional NPP, and a drying trend in the Southern Hemisphere has decreased NPP in that area, counteracting the increased NPP over the Northern Hemisphere."

These results were surprising since earlier studies had shown increasing plant carbon capture with rising temperatures in the 80s and 90s. However temperatures since 2000 have been the highest in modern records and accompanying droughts have apparently cut into global plant growth.

Again the Science article is not open access, but this EurekAlert release has some more information on the results and their implications.

While longer growing seasons and higher atmospheric carbon dioxide levels may favor more carbon fixation in some northerly regions, more of the globe is water-limited and more drought could hurt total carbon fixation more than warming trends would boost it. As the authors say in their abstract, "A continued decline in NPP would not only weaken the terrestrial carbon sink, but it would also intensify future competition between food demand and proposed biofuel production."

Plankton Declining With Warming Seas

Researchers from Dalhousie University studied the concentrations of phytoplankton in the oceans. Writing in Nature report "declines in eight out of ten ocean regions, and estimate a global rate of decline of ~1% of the global median per year". "We conclude that global phytoplankton concentration has declined over the past century" and "long-term declining trends are related to increasing sea surface temperatures." Since phytoplankton, minute plants, "account for approximately half the production of organic matter on Earth" this could be bad news.

Marine phytoplankton

According to a Reuters story, "The study estimates the decline in marine algae has been approximately 40 percent since 1950." Half of all photosynthetic carbon fixation, cut by 40%!? That's significant and scary.

The story quotes study co-author Boris Worm: "I think that if this study holds up, it will be one of the biggest biological changes in recent times simply because of its scale. The ocean is two-thirds of the earth’s surface area, and because of the depth dimension it is probably 80 to 90 percent of the biosphere. Even the deep sea depends on phytoplankton production that rains down. On land, by contrast, there is only a very thin layer of production."

Here is an excellent release in Science Daily summarizing the report.

Yield Reductions in China?

A review paper in Nature by Shilong Piao et al. assesses "the impacts of historical and future climate change on water resources and agriculture in China. They find that in spite of clear trends in climate (especially temperature), overall impacts are overshadowed by natural variability and uncertainties in crop responses and projected climate, especially precipitation. In a best-case scenario, crop production is constant, whereas the worst-case scenario suggests that production could fall by about 20% by 2050." (From Editor's Summary.)

A Reuters article quotes further from the paper, "Countrywide, a 4.5 percent reduction in wheat yields is attributed to rising temperatures over the period 1979-2000," and says "They forecast that rice yields would decrease by 4 to 14 percent, wheat by 2 to 20 percent and maize by zero to 23 percent by the middle of the 21st century."

(Grist carries an AFP story about this research.)

What Does It Mean?

These results from several unrelated fields of research suggest that we should be concerned that continued warming will negatively affect both wild plants (which act as a carbon dioxide sink) and agriculture (fundamental to social stability).

If forests, grasslands, phytoplankton in the sea and other ecosystems absorb less of the CO₂ we release by unrestrained burning of fossil fuels, then atmospheric CO₂ levels may rise faster than models currently predict.

If higher temperatures and drought reduce agricultural output more land will have to be brought under the plow. Such land-use changes usually release significant additional carbon dioxide.

We should significantly increase spending on agronomy and plant breeding, especially in Africa, India and East Asia, if we want to maintain the yields we have.

How Much Warming Are We Asking For?

noreply@blogger.com (David) — Mon, 19 Jul 2010 19:08:00 +0000

"A New Epoch"

A recent report from the U.S. National Research Council does not mince words.

"Emissions of carbon dioxide from the burning of fossil fuels have ushered in a new epoch where human activities will largely determine the evolution of Earth’s climate. Because carbon dioxide in the atmosphere is long lived, it can effectively lock the Earth and future generations into a range of impacts, some of which could become very severe. Therefore, emissions reductions choices made today matter in determining impacts experienced not just over the next few decades, but in the coming centuries and millennia." [From the executive summary]

Key points of the report:

Because CO₂ persists so long in the atmosphere, our emissions today and over the rest of the century will have profound effects on Earth's systems for centuries or even millennia to come.
To achieve atmospheric CO₂ stabilization at any given level, emissions will have to be cut by more than 80% from current rates. The longer we wait to make those cuts the higher the level will be when it stabilizes.
Global average temperatures can be correlated with atmospheric levels of carbon dioxide, so we can make predictions of future warming from projections of future emissions.
A growing body of research allows specific likely changes in Earth's systems to be forecast based on projected average global temperatures.
"The report concludes that certain levels of warming associated with carbon dioxide emissions could lock the Earth and many future generations of humans into very large impacts; similarly, some targets could avoid such changes."

Projected climate impacts

The report, "Climate Stabilization Targets: Emissions, Concentrations, and Impacts Over Decades to Millennia", addresses this situation by providing estimates of the impacts from various levels of global warming and CO₂ emissions. The authors hope policymakers will take advantage of this information.

The report estimates changes in precipitation, streamflow, wildfires, crop yields, and sea level rise that can be expected with different degrees of warming. It also estimates the average temperature increases that would be likely if CO2 were stabilized in the atmosphere at various target levels. However, the report does not recommend any particular stabilization target, noting that choosing among different targets is a policy choice rather than strictly a scientific one because of questions of values regarding how much risk or damage to people or to nature might be considered too much. [From the press release]

(The full report is available here You have to enter an email address on a form to download the free PDF. A PDF of executive summary here.)

The report tries to convey a sense of urgency by reminding us that "climate change due to carbon dioxide will persist many centuries". This is because CO₂ remains so long in the atmosphere. Even if we were to reduce our emissions immediately the excess CO₂ we have already put into the atmosphere will continue to drive changes in the Earth's climate for decades or even centuries to come.

And the authors note that "Depending on emissions rates, carbon dioxide concentrations could double or nearly triple from today’s level by the end of the century, greatly amplifying future human impacts on climate." Translation: if you think the consequences we have already set in motion by past and current emissions are unattractive, just imagine the impact of annual emissions several fold higher continuing for many decades.

The Future

What will those quantities of carbon dioxide mean in terms of actual warming, and what will that warming do to the environment and society? First, the report estimates the warming we are buying with our current and future emissions. This table shows estimated eventual warming at various "stabilization" levels of CO₂. (Today's level is about 390 ppm, but of course we are not stabilizing at that level.)

Here are some of the corresponding impacts the report predicts:

"For each degree (°C) of global warming:
- 5-10% changes in precipitation in a number of regions
- 3-10% increases in heavy rainfall
- 5-15% yield reductions of a number of crops
- 5-10% changes in streamflow in many river basins worldwide
- About 15% and 25% decreases in the extent of annually averaged and September Arctic sea ice, respectively
For warming of 2°C to 3°C, summers that are among the warmest recorded or the warmest experienced in people’s lifetimes, would become frequent.
For warming levels of 1°C to 2°C, the area burned by wildfire in parts of western North America is expected to increase by 2 to 4 times for each degree (°C) of global warming."

We can fix it, right?

To make warming level off at any particular global temperature, the concentration of carbon dioxide would have to be stabilized at some level. But because human-caused emissions are rising sharply, and because past emissions will linger in the atmosphere and have continuing effects, annual emissions would have to be cut by at least 80% to get our production of greenhouse gases back in line with what the Earth's systems can deal with. Only by keeping emissions at the level the planet can absorb can we stabilize the atmospheric concentration of CO₂.

Note: this is only talking about stabilizing the atmospheric concentration of carbon dioxide at some higher level in the future. There is no way to turn back the emissions clock to get to lower levels of CO₂ that would commit us to less warming. (The report explicitly didn't consider "geoengineering" to get carbon out of the atmosphere.)

So far, some rich nations have collectively proposed to cut emissions by about 12.5% below 1990 levels by 2020 (see this previous post). Other countries, however, plan to keep increasing emissions. And the promised cuts are not firm. Some have not even been officially embodied in law or policy. There is still vague talk about cutting emissions 50% below 1990 levels by 2050. But even that would result in more CO₂ accumulating in the atmosphere every year. Our 1990 emissions, about 20 gigatonnes of carbon dioxide, were already far more than natural systems could absorb, and even half that level would exceed the capacity of natural sinks and result in continued accumulation.

So 50% cuts from 1990 global carbon dioxide emissions would not make atmospheric CO₂ concentrations level off. This report considers what warming would result when and if we eventually get CO₂ in the atmosphere to stabilize at some future higher level. If we don't achieve such stabilization, warming will continue beyond the temperatures discussed in this study.

We probably can't go back again to earlier historical CO₂ levels. The only question is what level we can get those CO₂ levels to stabilize at, if any. That will determine what degree of global warming we will eventually have.

Our legacy

If you think the heat waves and other very minor consequences we have seen with just one degree of warming are a cause for concern, you ain't seen nothing yet. We are already committing our great grandchildren to several degrees of additional warming--maybe three or four more degrees--a very different Earth. The question is how much we further we are willing to go beyond that.

[All quotations and images are from "Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia" by the Committee on Stabilization Targets for Atmospheric Greenhouse Gas Concentrations of the Board on Atmospheric Sciences and Climate Division on Earth and Life Studies, National Research Council of the National Academies. Published by The National Academies Press, prepublication copy, at http://www.nap.edu/catalog/12877.html. The report is copyright © National Academies of Sciences.]

The Temperature's Rising--It Isn't Surprising

noreply@blogger.com (David) — Mon, 12 Jul 2010 23:11:00 +0000

Weather and Climate--Uncomfortable Truths

Recent heat waves in Eastern North America and Eastern Asia call attention to some sticky trends. While it's important to distinguish between "weather", what you see outside at a particular place and time, and "climate", long-term average weather, a number of scientific studies say that future decades will probably see many more heat waves like these.

Sections below cover: Predictions from models, recent weather records, health effects, and other effects of hot weather.

Previous "record" heatwaves will become commonplace

Noah Diffenbaugh and Moetasim Ashfaq at Stanford report in "Intensification of hot extremes in the United States", in press at Geophysical Research Letters (GRL), that what was a record heat wave during the 20th century could occur several times a decade over the next 30 years.

In the study, Diffenbaugh and Ashfaq used two-dozen climate models to project what could happen in the U.S. if increased carbon dioxide emissions raised the Earth's temperature by 1.8 degrees Fahrenheit (1 degree Celsius) between 2010 and 2039 ... . ... "Our results suggest that limiting global warming to 2 degrees C above preindustrial conditions may not be sufficient to avoid serious increases in severely hot conditions," Diffenbaugh said. ... According to the climate models, an intense heat wave - equal to the longest on record from 1951 to 1999 - is likely to occur as many as five times between 2020 and 2029 over areas of the western and central U.S. The 2030s are projected to be even hotter. "Occurrence of the longest historical heat wave further intensifies in the 2030-2039 period, including greater than five occurrences per decade over much of the western U.S. and greater than three exceedences per decade over much of the eastern U.S.," the authors wrote. [Quoting from Woods Institute post.]

Image from Diffenbaugh and Ashfaq via Woods Institute post

A post at The Woods Institute for the Environment at Stanford University summarizes their recent research. The paper hasn't appeared yet at GRL (and will probably be behind a pay wall there when it is published).

Other similar findings

The 2009 report of the U.S. Global Change Research Program, Global Climate Change Impacts in the U.S., found "Many types of extreme weather events, such as heat waves and regional droughts, have become more frequent and intense during the past 40 to 50 years." "Recent studies using an ensemble of models show that events that now occur once every 20 years are projected to occur about every other year in much of the country by the end of this century. In
addition to occurring more frequently, at the end of this century these very hot days are projected to be about 10°F hotter than they are today."

Hayhoe et al. report in Climate change, heat waves, and mortality projections for Chicago (in press) that events like the 1995 heat wave that tortured Chicago "could occur every other year on average under lower emissions and as frequently as three times per year under higher." Considering an event like the European Heat Wave of 2003, "Between mid- and end-of-century, there could be as many as five such events under lower, and twenty-five under higher emissions." The abstract:

Over the coming century, climate change is projected to increase both mean and extreme temperatures as heat waves become more frequent, intense, and long-lived. The city of Chicago has already experienced a number of severe heat waves, with a 1995 event estimated to be responsible for nearly 800 deaths. Here, future projections under SRES higher (A1FI) and lower (B1) emission scenarios are used to estimate the frequency of 1995-like heat wave events in terms of both meteorological characteristics and impacts on heat-related mortality. Before end of century, 1995-like heat waves could occur every other year on average under lower emissions and as frequently as three times per year under higher. Annual average mortality rates are projected to equal those of 1995 under lower emissions and reach twice 1995 levels under higher. An 'analog city' analysis, transposing the weather conditions from the European Heat Wave of 2003 (responsible for 70,000 deaths across Europe) to the city of Chicago, estimates that if a similar heat wave were to occur over Chicago, more than ten times the annual average number of heat-related deaths could occur in just a few weeks. Climate projections indicate that an EHW-type heat wave could occur in Chicago by mid-century. Between mid- and end-of-century, there could be as many as five such events under lower, and twenty-five under higher emissions. These results highlight the importance of both preventive mitigation and responsive adaptation strategies in reducing the vulnerability of Chicago's population to climate change-induced increases in extreme heat.

Graph from Global Climate Change Impacts in the United States, page 118.

If you think this year has been hotter than you remember, NASA agrees

We have just experienced the hottest January to June in the NASA dataset, which goes back to 1880. "It is likely that global temperature for calendar year 2010 will exceed the 2005 record, but that is not certain if a deep La Nina develops quickly." (From the June 1, 2010, Revised draft of Dr. James Hansen's "Global Surface Temperature Change" paper.)

12-month mean global temperature is now the warmest
in instrumental record. 60 and 132-month (5 and 11-year)
means minimize tropical and solar variability. These charts
and the caption are from Hansen's poster, available here (ppt).

(Joe Romm's Climate Progress blog summarizes the data from various sources in this post.)

More than inconvenient: People die in heat waves, but you'll probably survive

Most discussions of heat waves point out that they are the deadliest weather events, with more people dying from heatwaves than from floods, cold or hurricanes. That is true. But most of the people that die in heat waves are the elderly and those with serious medical conditions. Other weather events kill more randomly.

Mortality may increase during heat waves, but the drop in mortality that may occur after heat waves suggest that some of those deaths may be "short-term forward mortality displacement". Some studies have shown that a large fraction of heat wave deaths may have been among people who would have died within a short time even without the extreme hot weather. (For example see Revich and Shaposhnikov, 2008.

Deaths in floods and hurricanes are not concentrated among the elderly who may have been on the point of death, but have broader age distributions. The elderly and ill do suffer more in cold weather, but there isn't the same evidence for forward mortality displacement.

More than just hot weather

Yes it will be hotter, and heat waves will be more frequent and more severe. But many other effects are correlated with temperature.

Insurance claims for lightning damage are strongly correlated with temperature. These will probably increase. Premiums will go up.
Crop damage from heat waves can be significant, especially if they happen during sensitive times like germination, flowering or pollination.
The incidence of several diseases, including Salmonella food poisoning and West Nile Virus, are correlated with high temperature events.
Heat waves can lead to crime waves, especially if they cause power blackouts.

Get used to a very different Earth

"We're getting a dramatic taste of the kind of weather we are on course to bequeath to our grandchildren," says Tom Peterson, Chief Scientist for NOAA’s National Climatic Data Center. (Quoted on The Project on Climate Science site.)

Thanks to Irving Berlin for the lyric of the song "Heat Wave" used for the title of this post. Hear here.

Rain Won't Go Away

noreply@blogger.com (David) — Sat, 19 Jun 2010 16:42:00 +0000

Recent deadly heavy rains in the U.S., France and China may be part of a long-term trend toward heavier downpours due to climate change. (See earlier post.)

If you can't see the video, watch it on YouTube here.

Scientists from the Met Office, the UK's national weather bureau, have published research showing that the changes in rainfall patterns already attributed to climate change will persist even if global greenhouse gas emissions are controlled.

"A team led by Peili Wu used a computer model to analyse how the Earth's water cycle could react to changes in future amounts of carbon dioxide in the atmosphere. It found that once carbon dioxide levels rise to a high level, even sharp reductions fail to prevent longlasting impacts on snow and rainfall." [Source: Guardian article.]

Our results suggest that relationships between precipitation and warming may significantly underestimate precipitation changes during periods of [greenhouse gas] stabilisation or reduction. The inertia due to the accumulated heat in the ocean implies a commitment to changes long after stabilisation. This effect must be taken into account when assessing the implications of various mitigation options for flooding, water supply, food production and human health.

Their model assumed substantial increases in atmospheric CO₂, up to a level of 1,000 ppm (up from today's 390 ppm and pre-industrial levels of 280 ppm) over many decades, then a rapid reduction back to 280 ppm. Because of the substantial amount of heat that would become trapped in the oceans, where it leads to increased rainfall, altered rainfall patterns would persist for a long time after CO₂ levels were reduced.

This model embodies an extreme hypothesis, but it makes an important point. Just fixing greenhouse gas emissions, which seems to be politically impossible anyway, does not reverse climate changes. Get used to a very different Earth.

A Hard Rain's A-Gonna Fall

noreply@blogger.com (David) — Sat, 19 Jun 2010 15:32:00 +0000

Researchers at the University of New Hampshire have analyzed 60 years' worth of National Weather Service rainfall records in nine Northeastern states and found that storms that produce an inch or more of rain in a day are coming more frequently. An increase in the frequency of extreme precipitation events
is one of the predicted impacts of a world warmed by heat-trapping
gases.

The researchers looked at several indicators of changing incidence of heavy rain events:

Frequency of 24-hour periods when one inch of rain fell at a particular weather station site (a "one-inch event")
Similarly, the occurrence of "two-inch events" and "four-inch events", when two or four inches fell at a site in 24 hours
The frequency of extreme precipitation events, defined as the top one percent of 24-hour precipitation measurements for each year. "Changes in the threshold of the 99th percentile of daily accumulations exemplify changes in precipitation intensity" (how much rain has to fall in 24 hours to put an event in the 99th percentile for the year?)
A third method was to define extreme precipitation events using recurrence intervals. They looked at the change in the amount of time between storms of a given magnitude.

According to each of the indicators studied extreme rainfall events have increased over the 50-year period. For 11 stations the records go back far enough to track such events from 1900 to 2007. For all of the indicators the increases at those stations since 1948 were faster than for the whole period 1900 to 2007.

The increase in more-intense rainfall was correlated with increases in temperature seen over the period. This suggests that further increases in temperature will correlate to further increases in the occurrence of heavy rainfall events.

They also found that over the whole 50-year study period rainfall in the Northeast has an overall increasing trend of about three-quarters of an inch per decade.

The study concludes that communities are likely to experience increased flooding due to intense storms (as they have this year, for instance) and that planning and expenditure to minimize the impacts of flooding will be increasing drains on the public purse.

The report, Trends in Extreme Precipitation Events for the Northeastern United States 1948-2007, is available in PDF here.

[Reposted from Science In Action.]

Thanks For All The Fish

noreply@blogger.com (David) — Wed, 19 May 2010 16:46:00 +0000

There is lots of research to show that we are already living in a very different earth from that of a century ago as far as fish stocks are concerned. Everyone is familiar with the concept of "all the fish in the sea." Well, 90% of those fish are gone.

A fascinating study recently published in Nature shows that the amount of fish landed in England and Wales per unit of fishing power has declined more than 90% over the past 120 years. Increases in fishing power of new boats and equipment do not result in additional landings because the fish are gone. We ate them.

Landings per unit power figures suggest that the availability of bottom-living fish for the fleet fell by 94% from 1889 to 2007. This implies a massive loss of biomass of commercially fished bottom-living fish from seas exploited by the UK fleet. The loss is particularly serious as it encompasses an entire component of the marine ecosystem rather than a single species.

The collapse in fisheries productivity is brought into sharp relief by the landings data. In 1889, a largely sail-powered fleet landed twice as many fish into the United Kingdom than the present-day fleet of technologically sophisticated vessels. One hundred years ago, in 1910, the fleet landed four times more fish into the United Kingdom than it does today.

The Nature paper cites a number of other studies using various methods, all of which conclude that the particular fish stocks they analyzed have declined 90% or more over the period they studied.

What about other fish--are they gone too?

Separately a recent UN Environmental Program study says that 30% of all fish stocks are classified as "collapsed"--they yield less than 10% of their former potential.

Only around 25 per cent of commercial stocks--mostly of low-priced species--are considered to be in a healthy or reasonably healthy state.

On current trends, some researchers estimate that virtually all commercial fisheries will have collapsed by 2050 unless urgent action is taken to bring far more intelligent management to fisheries north and south.

Will governments and fishers get together and set up management systems that could allow stocks to recover, or avoid wiping out remaining stocks? On past form, don't bet on it. The UNEP study says better management could allow stocks to recover, would increase landings, and would increase the total value of landings and fishing household incomes substantially. But . . .

The study also estimates that the total value of the 80 million tonnes of fish caught is about US$85 billion annually. Of this fishing households see income of about US$35 billion. But governments dole out subsidies totaling over US$27 billion, three-quarters of all fishing household income!

Governments and fishing organizations are willing to take $27 billion of taxpayers' money to be sure that in a few decades there will be practically no fish left in any major fishery. Ten percent or less of the quantity of fish that were there 100 years ago is not much.

Here is a Reuters story about the results of the study from Nature.

[photo of fishing boat from adstream via flickr http://www.flickr.com/photos/adstream/1537402364/]

An Earth Too Hot For Humans?

noreply@blogger.com (David) — Thu, 06 May 2010 19:21:00 +0000

In worst-case but possible warming scenarios, much of Earth could become too hot for human habitation. That's the gist of recent research by Steven C. Sherwood of the Climate Change Research Centre, University of New South Wales and Matthew Huber of the Purdue Climate Change Research Center published in PNAS (Abstract here, article behind pay wall).

This graphic shows areas that could be too hot for humans in one scenario (12 degrees C over pre-industrial levels, I think). The too-hot areas include much of Africa, the American Southeast, Australia, Brazil India, Oceana and eastern China.

From their abstract:

Despite the uncertainty in future climate-change impacts, it is often assumed that humans would be able to adapt to any possible warming. Here we argue that heat stress imposes a robust upper limit to such adaptation. Peak heat stress, quantified by the wet-bulb temperature T_W, is surprisingly similar across diverse climates today. T_W never exceeds 31 °C. Any exceedence of 35 °C for extended periods should induce hyperthermia in humans and other mammals, as dissipation of metabolic heat becomes impossible. While this never happens now, it would begin to occur with global-mean warming of about 7 °C, calling the habitability of some regions into question. With 11–12 °C warming, such regions would spread to encompass the majority of the human population as currently distributed. Eventual warmings of 12 °C are possible from fossil fuel burning. One implication is that recent estimates of the costs of unmitigated climate change are too low unless the range of possible warming can somehow be narrowed.

Translation (mostly from Purdue press release):

The researchers calculated the highest tolerable "wet-bulb" temperature and found that this temperature could be exceeded for the first time in human history in future climate scenarios if greenhouse gas emissions continue unabated.

"Although areas of the world regularly see temperatures above 100 degrees, really high wet-bulb temperatures are rare," co-author Huber said. "This is because the hottest areas normally have low humidity, like the 'dry heat' referred to in Arizona. When it is dry, we are able to cool our bodies through perspiration and can remain fairly comfortable. The highest wet-bulb temperatures ever recorded were in places like Saudi Arabia near the coast where winds occasionally bring extremely hot, humid ocean air over hot land leading to unbearably stifling conditions, which fortunately are short-lived today."

The challenges presented by the future climate scenarios are daunting in their scale and severity, he said.

"Whole countries would intermittently be subject to severe heat stress requiring large-scale adaptation efforts," Huber said. "One can imagine that such efforts, for example the wider adoption of air conditioning, would cause the power requirements to soar, and the affordability of such approaches is in question for much of the Third World that would bear the brunt of these impacts. In addition, the livestock on which we rely would still be exposed, and it would make any form of outside work hazardous."

"We found that a warming of 12 degrees Fahrenheit would cause some areas of the world to surpass the wet-bulb temperature limit, and a 21-degree warming would put half of the world's population in an uninhabitable environment," Huber said. "When it comes to evaluating the risk of carbon emissions, such worst-case scenarios need to be taken into account."

"The wet-bulb limit is basically the point at which one would overheat even if they were naked in the shade, soaking wet and standing in front of a large fan," lead author Sherwood said. "Although we are very unlikely to reach such temperatures this century, they could happen in the next."

On the other hand, the 22nd century is a long time from now. Who knows what technology will be available to keep people and livestock comfortable even in lethal environments. But it could be a very different Earth.

[Update 2013-02-25 1800GMT:
Recent research by NOAA scientists suggests warming is already reducing capacity of people to work in many regions, and could have severe effects by 2050. "This planet will start experiencing heat stress that's unlike anything experienced today," says one of the authors of the study in Nature Climate Change. (Abstract here; article behind Nature paywall.) Here is a Reuters item about the research.]

Ocean Acidification--A Basic Environmental Change

noreply@blogger.com (David) — Sat, 24 Apr 2010 22:20:00 +0000

One inevitable long-term change due to humanity's two-century carbon orgy is seen in the chemistry of seawater. An upcoming report from the U.S. National Academy of Sciences reviews the issues (access report summary here, registration required).

Ocean Acidification

The pH of the ocean surface waters is around 8.1. Thus oceans are not acid, they are basic. A better term might be "ocean debasification". Be that as it may, about one-third of the carbon dioxide we have been dumping into the atmosphere over the past 200 years has ended up dissolving in the oceans, increasing their surface pH from 8.2 to 8.1, and model projections show an additional 0.2-0.3 drop by the end of the century, "even under optimistic scenarios". "The rate of this change exceeds any known change in ocean chemistry for at least 800,000 years." Not good.

"Atmospheric CO₂ increased over thousands of years during the glacial/interglacial cycles of the past 800,000 years, slow enough for the CaCO₃ cycle to compensate and maintain near constant pH." But currently "the concentration of atmospheric CO₂ is rising too rapidly for natural, CaCO₃-cycle processes to maintain the pH of the ocean. As a consequence, the average pH of the ocean will continue to decrease as the surface ocean absorbs more atmospheric CO₂."

"It is currently not known if and how various marine organisms will ultimately acclimate or adapt to the chemical changes resulting from acidification, but existing data suggest that there likely will be ecological winners and losers, leading to shifts in the composition and functioning of many marine ecosystems. It is also not known how these changes will interact with other environmental stressors such as climate change, overfishing, and pollution. Most importantly, despite the potential for socioeconomic impacts to occur in coral reef systems, aquaculture, fisheries, and other sectors, there is not currently enough information to assess these impacts, much less develop plans to mitigate or adapt to them." Like driving fast at night on a curvy road with no headlights.

The NAS report recommends a lot more research funding on this topic, so we will at least have a flashlight to illuminate the road ahead, since it doesn't look like anyone is willing to consider the option of slowing down.

This Wikipedia article gives links to additional information sources.

A World Without Ice--Book Review

noreply@blogger.com (David) — Sat, 17 Apr 2010 23:16:00 +0000

"Ice is a sleeping giant that has been awakened, and if we fail to recognize what has been unleashed, it will be at our peril." (Page 130.)

Henry Pollack's A World Without Ice (Avery/Penguin 2009) is not a bad book, but I can't recommend it wholeheartedly. It has a lot of fascinating information in it, from reliable resources (with footnotes--Pollack is Professor of Geophysics Emeritus in the Department of Geological Sciences at the The University of Michigan). But that information is jumbled together and in a few places repetitive. There is not a well-defined theme, story or argument.

Professor Pollack uses information about the Earth's ice deposits of the past, present and future to tell the story of global climate change. But he does not hesitate to include any other information he has at hand, and his chapters wander.

"Nature's best thermometer, perhaps its most sensitive and unambiguous indicator of climate change, is ice. When ice gets sufficiently warm, it melts. Ice asks no questions, presents no arguments, reads no newspapers, listens to no debates. It is not burdened by ideology and carries no political baggage as it crosses the threshold from solid to liquid. It just melts." (Page 114.) "If at times in the past ice ruled the world, then in the warm centuries of the future, seawater--ice's playmate on the global hydrological seesaw--will be the formidable adversary of human life on Earth." (Page 230.)

Any reader will learn some interesting facts, and hear some convincing arguments about global warming. But Professor Pollock could have benefited from a stricter editor.

Carbon Dioxide Like Nuclear Waste--It's Forever

noreply@blogger.com (David) — Thu, 08 Apr 2010 20:47:00 +0000

If you can't see the video, watch it on YouTube here.

The Rising Sea--Book Review

noreply@blogger.com (David) — Sat, 27 Mar 2010 18:44:00 +0000

The Rising Sea by Orrin Pilkey and Rob Young (details here from Island Press, or check this link), is well worth reading. Pilkey (Professor Emeritus of Earth Sciences, and Founder and Director Emeritus of the Program for the Study of Developed Shorelines within the Nicholas School of the Environment at Duke University) and Young (Professor of Geosciences at Western Carolina University) know the science of the shoreline in great detail, and convey their story in relatively accessible prose.

They aren't writing primarily about "global warming" or "climate change", but about the undeniable and inexorable rise in sea levels around the globe, and some of the predictable consequences. They decry the shortsightedness of coastal development that ignores future coastal changes for present gain, and they are no friends of the U.S. Army Corps of Engineers.

Their technical content shouldn't fluster anyone who took science courses in high school (and paid attention) and their message is clear from their prose if you didn't. The reader should come away with at least an inkling of the issues of geographic change, habitat loss and economic disruption that are developing at the interface between shoreline development and rising seas and flood levels.

Sea level rise is in the news often (as seen in two items in this issue of HaraBara Daily Brief) but is usually remote from the daily concerns of most of us. The very different Earth of our grandchildren will see it as a significant issue and cause of vast public expenditure.

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