Last week, the fragility of that thin blue shield was underscored by the news that we've reached a daily average of 400 parts per million (ppm) of carbon dioxide in our atmosphere. That's the highest level in at least 3 million years. In less than two centuries, we've increased atmospheric CO2 by 42 percent -- by burning fossil fuels, degrading our forests, and disturbing our soils. And it's still going up.

Although the notion of sending Congress, the president, and every other decision maker into outer space has some appeal, it's not exactly the most practical thing. Yet the climate crisis demands the same kind of cognitive shift experienced by astronauts: We cannot let that CO2 ppm number keep ticking up, and the best way to stop it is to stop burning fossil fuels and replace them with renewable energy as fast as we can.

Unfortunately, although President Obama has spoken eloquently about the climate crisis, the energy policies of his administration too often say "business as usual," not "cognitive shift." Here are just three examples:

First, on the same day that the 400-ppm milestone was reported, the administration released its National Strategy for the Arctic Region. Ironically, although the report correctly notes that the Arctic will be severely affected by climate disruption, it also includes talking points that could have come straight out of the Bush administration, including this sentence:

Continuing to responsibly develop Arctic oil and gas resources aligns with the United States "all of the above" approach to developing new domestic energy sources, including renewables, expanding oil and gas production, and increasing efficiency and conservation efforts to reduce our reliance on imported oil and strengthen our nation's energy security.

Wrong. Although the parenthetical nod to renewables is nice, any "all of the above" policy that furthers our dependence on oil and gas doesn't strengthen our energy security. Instead, it increases our climate insecurity. As Shell Oil learned the hard way, there are many good reasons why it's a bad idea to attempt offshore drilling in the Arctic. We only need this one, though: If we are serious about addressing the climate crisis, then oil under the Arctic Ocean needs to stay there.

Example #2 -- Just yesterday, the Bureau of Land Management released new proposed regulations for fracking natural gas on public lands. The new rules are disappointing for many reasons: Drillers won't be required to disclose what chemicals they're using, there is no requirement for baseline water testing, and there are no setback requirements to govern how close to homes and schools drilling can happen. Once again, though, the policy documents an even bigger failure to grasp a fundamental principle: If we're serious about the climate crisis, then the last thing we should be doing is opening up still more federal land to drilling and fracking for fossil fuels.

Lastly, of course, there is the issue of tar-sands crude and the Keystone XL pipeline. I've written many times about the risks of both, but the bottom line is that allowing tar sands extraction to expand will undermine the progress that has been made to reduce carbon pollution elsewhere in the economy.

The good news: We still have time to act. Through clean-energy technology, smart policies, and responsible leadership, we can spare future generations the "worst-case scenario" for climate disruption. To make that happen, though, the biggest change has to occur on the inside first -- a cognitive shift away from the fossil-fuel world we've known our entire lives.

We can't literally escape gravity to stare in awe at our amazingly beautiful planet and suddenly comprehend what's at stake -- but we can make the journey in our hearts and minds. Once we do -- whether we're sitting behind a desk in the Oval Office or on a back-porch swing in Salina, Kansas -- we can see the better world that lies beyond coal, oil, and gas.

Six months ago, Sandy took it apart.

By the time it hit the eastern seaboard, Sandy was an unusual hybrid of a post-tropical cyclone and an upper level low system. "Superstorms" like Sandy could develop without the influence of climate disruption, but warmer ocean temperatures and a shifting jet stream unquestionably have increased the odds. The scariest thing about Sandy is that such a freak of weather may no longer be so freakish.

A new norm of extreme weather is a daunting prospect. In Sandy's case, the damage to my childhood home was part of the worst U.S. natural disaster since hurricanes Katrina and Rita -- much more than $50 billion in damages and at least 72 deaths. But Sandy also destroyed something intangible -- our complacency. No longer can we assign the consequences of climate disruption to some distant future. When Sandy struck, the future rose with the sea and smashed into us head on. The question it left behind was this: What do we do about it?

For the past 100 days, Sierra Club members and supporters have answered that question loudly and clearly. We gathered in Washington, D.C., for the largest climate rally in history. We held town hall meetings and grassroots rallies across the country. And we helped send more than a million messages to Barack Obama -- telling him that we want bold action on climate disruption.

For his part, the president answered Sandy's challenge by talking about the climate crisis in his strongest words yet, both in the State of the Union and his inaugural address.

The president's words were welcome, but words will not be enough. Here are five critical actions we need him to take:

1. Reject the toxic Keystone XL pipeline.
2. Protect our water from coal plant pollution.
3. Close loopholes on fracking and protect our wildlands from oil and gas development.
4. Finalize strong standards for cleaner tailpipe emissions.
5. Move forward with standards against industrial pollution.

Each of these actions is within President Obama's power right now. If he's serious about addressing climate disruption, not one of them is optional.

Meanwhile, we have to keep our own voices raised. If you haven't added yours yet -- you can do it here. Together, we will move forward on climate -- and we need our president to lead the way.

It was also only part of the story.

The other part -- also a really big deal -- is that Southern California is rapidly locking in new sources of energy to replace dirty fossil fuels. One of them -- the Antelope Valley Solar Projects that officially broke ground on Friday -- represents large-scale renewable energy technology at its best and its brightest. When completed in 2015, these solar projects will provide 579 megawatts of clean energy (enough to power about 400,000 homes). Every one of those megawatts will displace energy that might otherwise come from dirty fossil fuels like natural gas. In the process, they'll eliminate more than 775,000 tons of carbon pollution per year (not to mention quite a lot of air and water pollution).

Fantastic as those stats are, though, they wouldn't mean as much if this project did not succeed in a couple of other important ways.

Here in the United States, we're lucky to have abundant renewable energy resources -- wind, sun, and hydro. In theory, it's enough to power our entire country several times over. But we need to be smart about where and how we access that energy. The rim of the Grand Canyon, for instance, would never be anyone's first choice for a wind farm.

In the case of Antelope Valley, the project has been a model of smart planning. In fact, Sierra Club volunteers worked closely with the developers almost from the beginning to improve the project. The project site was private land that had no threatened or endangered species. It's located near existing transmission lines. It will require a lot less water than the previous use for the land -- growing alfalfa.

Another way the Antelope Valley Solar Projects succeed is economically. Here's the proof: Early this year, the original developer of the project, SunPower, was acquired by MidAmerican Renewables, a subsidiary of MidAmerican Energy Holdings Company, which is controlled by Berkshire Hathaway. The primary shareholder, chairman, and CEO of Berkshire Hathaway, of course, is Warren Buffett, who is considered the most successful investor of the 20th century. MidAmerican has a portfolio of more than 1,830 megawatts of renewable energy assets, including wind, geothermal, solar, and hydro assets.

The next time someone tries to tell you that renewable energy isn't a good investment, point out that it's good enough for Warren Buffett. (Before you send the Oracle of Omaha a clean-energy mash note, though, be sure to read the just-published Sierra magazine article about a more problematic part of his portfolio. Mr. Buffett should take care to avoid the carbon bubble and move out of dirty fuels entirely.)

The Antelope Valley Solar Projects are part of a remarkable surge in solar solutions. Last month, all of the new power-generation capacity added in the U.S. came from solar power. In the first three months of 2013, we added twice as much new solar capacity to the U.S. grid as in all of 2012. Projects like the ones in Antelope Valley are great for the environment and for our clean-energy future. If they show dirty fuel investors how they can profit from clean energy instead, that's good, too.

In 1849, an eleven-year-old boy moved with his family to the United States. More than four decades later, that boy co-founded the Sierra Club and served as its president for the next 22 years. Like many great Americans, John Muir was an immigrant. It is only because he was able to take advantage of the opportunities in his adopted country that the Sierra Club exists at all.

Today, however, the American immigration system is broken. It forces approximately 11 million people to live outside the prevailing currents of our society. Many of them work in the fields, mop floors, care for other people's children, and take low-wage jobs to support their families. Many work in jobs that expose them to dangerous conditions, chemicals and pesticides, and many more live in areas with disproportionate levels of toxic air and water pollution.

The 20 million Americans with family members whose legal status is in limbo share the Sierra Club's concerns about climate and the environment. For example, our own polls indicate that Latinos support environmental and conservation efforts with even greater intensity than the average American: 90 percent of Latino voters favor clean energy over fossil fuels. A California study found that 74 percent of Asian-Americans, the fastest growing group in America, accept climate science. Yet, significant numbers of these stakeholders and change agents have been denied their civil rights in the public arena.

The Sierra Club is committed to partnering with all who share our urgent concerns about advancing our democracy and fighting the climate crisis. It is time for us to work together.

That is why the Sierra Club Board of Directors has voted to offer our organization’s strong support for a pathway to citizenship for undocumented immigrants. Such a pathway should be free of unreasonable barriers and should facilitate keeping families together and uniting those that have been split apart whenever possible.

For the Sierra Club and the environmental movement to protect our wild America, defend clean air and water, and win the fight against climate disruption, we must ensure that the people who are the most disenfranchised and the most affected by pollution have the voice to fight polluters and advocate for climate solutions without fear.

This isn't the first time that the Sierra Club has taken a stand on a critical issue. In 1993, the Club opposed the North American Free Trade Agreement, a controversial position, but one that has proven to be the right choice. We did not think it would be good for workers or the environment, and it hasn't been. In fact, NAFTA has been a major driver of undocumented immigration into the U.S. from Mexico and Central America.

More recently, the Club has challenged the Real ID Act, which allows the Department of Homeland Security to waive 36 federal laws -- including the Endangered Species Act, the Clean Water Act, and the Wilderness Act. That ill-conceived suspension of bedrock environmental laws has been used to construct border walls in the Southwest with little regard to their effect on wildlife and habitats nor their cost in human lives. Dan Millis, our Sierra Club Borderlands campaign organizer, was famously given a littering ticket by the U.S. Fish and Wildlife Service for leaving life-saving bottles of water on federally protected land in the Sonoran desert.

We cannot solve either the climate crisis or our broken immigration system by acting out of fear or by supporting exclusion. One of our nation's greatest strengths is the contribution that generations of immigrants have made to our national character. If we are serious about solving the climate crisis and protecting our democracy, then we need to work with the hardworking men and women who want to play by the rules and play a part in building a healthy, safe, and prosperous future for our country.

A just-released report from Oil Change International, "Cooking the Books," shows that the carbon emissions from the Keystone XL pipeline alone would be enough to undermine most of the progress that we've made to date on limiting climate-disrupting carbon pollution. If approved, the Keystone XL tar sands pipeline would be responsible for the carbon-pollution equivalent of more than 37.7 million cars -- every single year. Between 2015 and 2050, Keystone XL's emissions would add up to more carbon pollution than the entire United States produced during 2011.

I'm an optimist. The strong fuel-economy standards from the Obama administration and the steady move away from coal-fired power plants have us heading, slowly, in the right direction. It's easy to be inspired by sights like last weekend's 16-mile march by the Moapa Band of Paiutes of southern Nevada from the polluting Reid Gardner coal plant to the site of their soon-to-be-built solar project, which will be the largest on tribal lands in the U.S.

Keystone XL, however, threatens to derail this kind of clean-energy progress with one stroke.

The State Department has asserted that the pipeline would result in "no substantive change in global greenhouse gas emissions." How did the State Department get it so wrong? Simple -- it assumed that Canada's tar sands will be developed regardless of whether Keystone XL is built. Talk about self-defeating, circular logic.

The truth is that we cannot afford to do anything that will make it easier for Big Oil to extract the tar sands, and Keystone XL certainly fits that bill. If it didn't, then its proponents would not be fighting so hard to get it built. The tar sands are not a path to energy independence -- they're a fast track to climate disaster.

Here's another important reason why Keystone XL must be stopped: The appalling risk it poses to the American people. The 22-foot gash in ExxonMobil's Pegasus tar sands pipeline in Arkansas puts that risk in sharp relief.

Here's how Riki Ott, a marine toxicologist and oil-spill health expert, explained the difference between tar sands crude and conventional oil to me:

Tar sands crude contains much higher concentrations of the ultrafine particles, or polycyclic aromatic hydrocarbons (PAHs), which are the long-term bad actors in terms of health issues. PAHs get inside cells and jam cell function, causing respiratory problems, reproductive problems, depressing immune system function, disrupting DNA coding, and more.

Tar sands bitumen contains 11 times more heavy metal than conventional oil, which is bad enough, but to make it possible to pump the sludgy bitumen, it must be mixed with another hydrocarbon, usually a natural gas distillate. When a tar sands spill happens, the distillate vaporizes, releasing toxic chemicals into the air. And if the heavy bitumen that's left behind gets into the water, it doesn't float like conventional oil -- it sinks.

In spite of the particular danger posed by a tar sands spill, no proven protocol exists for cleaning one up. We don't even know whether it's even possible to completely clean one up. Almost three years and a billion dollars after the tar-sands disaster that contaminated Michigan's Kalamazoo River, there is still bitumen on the riverbed.

Every day, more Americans become aware of just how extreme and dangerous a fuel tar sands crude really is. Last week, at the only public hearing on Keystone XL that the State Department will hold, hundreds of people testified about the pipeline. According to the New York Times, though, those who spoke out against it outnumbered proponents by at least 12 to 1.

President Obama cannot use ignorance as an excuse. He cannot approve Keystone XL and still claim to be moving forward on climate. As the Oil Change International report makes clear, he would in fact be cancelling out much of the progress on climate disruption that his administration has already achieved.

Today is Earth Day. Today is also the last day you can submit your comment to President Obama and the State Department. Do it now, please.

Seeing a Sierra Club leader and volunteer alongside the other honorees was great, but I confess to being a little extra proud this time. Greg comes from my old Jersey Shore stomping grounds.  My folks belong to the Ocean County Group, and they've gotten to know Greg pretty well (one unhappy thing they have in common is that Superstorm Sandy wrecked their homes). Greg was recognized in part for his work on post-Sandy recovery efforts, although he says the real credit should go to "all the dedicated NJ Sierra Club activists and supporters."

At the White House, here's what Greg had to say about the Club's approach: "Our governor likes to talk about being 'Jersey strong.' The Sierra Club thinks we should be 'Jersey smart.'" One way some beachfront communities haven't been too smart is by using lumber harvested from the Brazilian rainforest to rebuild beach boardwalks that were destroyed by Sandy. Noting that deforestation is the second-largest contributor to climate disruption after greenhouse gases, Greg said, "That's kind of like feeding the dog that just bit your hand."

Thanks to Greg and his fellow "Jersey-smart" activists, though, some towns have switched their plans and chosen to rebuild with sustainably sourced lumber or with a composite of wood and recycled plastic.

Congratulations to Greg Auriemma and to all the hard-working volunteers in the Ocean County Group and in Sierra Club chapters and groups across the nation. Not only do you make us proud, you're making a difference. 

Sierra Club organizer Glen Hooks, who grew up about 20 miles southeast of Mayflower, in Gravel Ridge, attended a meeting for the displaced families at Mayflower High School: "I had to really stare down some ExxonMobil goons who told me to leave because it was a private meeting. I politely explained that it was a meeting in a public building about a public subject with numerous public officials in attendance, and that I was planning to stay."

Glen's soft-spoken, but he's not easily intimidated. Arkansas Business Journal named him an "Eco-Hero of the Year" for his work in helping to stop new coal-fired power plants. During the Mayflower meeting, Glen listened as an ExxonMobil executive apologized to the families and said that the focus was on safety and helping the homeowners. "The meeting then moved into a phase where ExxonMobil met with individual family members about their claims in a side room guarded by no fewer than six uniformed police officers."

Here's something that ExxonMobil probably didn't tell those homeowners: In 2010, it was fined $26,200 by the U.S. Department of Transportation's Pipeline and Hazardous Materials Safety Administration for failing to regularly inspect each point where the Pegasus line crosses under a navigable waterway.

This is a pipeline that crosses under the Mississippi River (just one of the places ExxonMobil failed to do inspections). It's hard to say which is more shocking: That "safety first" ExxonMobil has been so cavalier about pipeline inspections or that it was fined such a pittance for its irresponsibility. By my calculation, $26,200 comes out to about .00009% of ExxonMobil's net income for 2010. Let's put that in perspective. If ExxonMobil's income were the same as the median family income in Faulkner County, Arkansas, which is where its pipeline leaked, then ExxonMobil's fine for putting the Mississippi River at risk would have been not quite four cents.

No matter how much ExxonMobil ends up spending to clean up the mess in Mayflower, the impact on its profit statement will be miniscule. Unfortunately, no amount of cash can buy peace of mind for the families whose homes were violated by tar sands. Tar sands crude is both more toxic and much harder to clean than ordinary crude. Just ask Enbridge, which has now spent almost $1 billion and two years trying to clean up the Kalamazoo River after the largest onshore oil spill in U.S. history. Enbridge has experience, too. There were 804 spills on its pipelines between 1999 and 2010.

No wonder ExxonMobil is doing everything it can to keep reporters and everyone else as far away from the Mayflower disaster as possible. The more the American public learns about the real cost of tar sands crude, the more opposition to the Keystone XL and other tar sands projects will increase.

Keystone XL opponents often point out that Americans assume all the risk of tar sands pipelines, while oil companies will rake in all the profit from tar sands exports. But let's be clear about the sort of risk we're talking about. If the pipeline is built, it's not a question of whether it will fail, but of when and where. We're not risking a disaster. Disaster is certain. We just don't know what the exact magnitude of the disaster will be. What if the Pegasus pipeline had failed under the Mississippi rather than in Mayflower?

Here's something we do know: The first Keystone XL disaster will be far worse than what happened in Mayflower, since TransCanada's pipeline will pump ten times as much tar sands crude as the Pegasus does.

I wish the disaster in Mayflower had never happened. Now that it has, though, I hope we heed its two biggest lessons: 1. How oil companies talk about safety has no connection to how they act. 2. The last thing you want to wake up and find in your backyard is a tar sands spill.

We have a few days left. Tell the president to keep his climate promises.

Just over two weeks. That's how much time we have left to tell President Obama he should reject the Keystone XL tar sands pipeline. We'll be living with the consequences of his decision for a lot longer. The climate pollution that mining the tar sands would create is reason enough not to approve Keystone, but last weekend's disaster in Arkansas is a glaring reminder of the other reason: Tar sands crude is much riskier to transport than conventional oil.

That the spill didn't happen in an even worse location is not much consolation to the residents of Mayflower who don't know when, or even if, they will be able to return to their homes. Many of them had no idea there was an oil pipeline in their neighborhood, much less that it was carrying tar sands crude. This was a tough way to find out.

When it comes to tar sands pipelines, what we don't know will hurt us. Here's what every American should know about tar sands pipelines:

1. Tar sands crude oil is much harder to clean up than conventional oil. That's because the bitumen that remains after benzene and other solvents evaporate is thick and heavy -- it sinks in water. Remember the Enbridge spill on the Kalamazoo River nearly three years ago? Despite a nearly $1 billion cleanup effort, 38 miles of the river remain contaminated.

3. Tar sands pipeline leaks are difficult to detect. It was 17 hours before the Enbridge pipeline that spilled on the Kalamazoo was finally shut off. We can be thankful that the spill in Mayflower was noticed in less than an hour, but that's only because a neighbor spotted it. Then again, it's hard to miss a river of oil flowing down your street.

4. Current pipeline regulations and spill-response methods are completely inadequate for the higher risks posed by tar sands. That's another reason to reject Keystone XL, but it's also a problem for existing older pipelines, like the one that spilled in Arkansas, that have started carrying tar sands during the past decade. The Sierra Club is part of a broad coalition of landowners, former and current government officials, environmental organizations, renewable energy promoters and sportsmen’s groups that has petitioned the EPA and the Department of Transportation's Pipeline and Hazardous Materials Safety Administration to develop stronger safety standards for tar sands pipelines and, in the meantime, put a moratorium on pumping tar sands crude.

Tragic as the disaster in Arkansas is, it could have been much worse. If the Keystone XL is built, it's a certainty that someday, somewhere, even more devastating spills will happen. It's only a matter of time. If you've already told President Obama where you stand, then ask your friends to do the same. There's no excuse in the world for pursuing extreme oil like tar sands when we could be investing in clean energy instead.

Fortunately, we don't have to rely on Congress for good news -- whether it's about cleaning up our air or protecting our public lands. So here's some of both kinds.

Start with the welcome announcement that President Obama has designated five new national monuments. They're all worthwhile, but two of them are also significant and long overdue additions to our wilderness heritage. The new Rio Grande del Norte National Monument includes 240,000 acres of northern New Mexico wilderness and represents hundreds of years of Native American and Hispanic culture. It also provides critical habitat for wildlife such as elk, deer, bighorn sheep, and many migratory birds. And the creation of San Juan Islands National Monument in Washington State protects 955 acres of what Obama's proclamation accurately describes as "a dramatic and unusual diversity of habitats with forests, woodlands, bluffs, inter-tidal areas, and sandy beaches." Not to mention orcas.

Both Rio Grande del Norte and the San Juans had strong local support for protection, both will provide major boosts to local economies, and both had previously been proposed as national conservation areas in Congress. The bills went nowhere. What was that word again? Sclerotic.

Here's some more good news that happened in spite of the current Congress, which has been more interested in weakening the Clean Air Act than enforcing it. During the past two decades, the air in our national parks has dramatically improved. But thanks to the Clean Air Act -- and our nation's move away from coal-fired power plants -- mountains are reappearing from the haze and smog. That's good news both for the millions of people who enjoy these parks and for the plants and wildlife that live in them. You can see a slideshow of "before and after" images from researchers at the Cooperative Institute for Research in the Atmosphere at Colorado State University.

In honor of Los Angeles, which has cleaned up its air dramatically during the past decade, and which is setting an example for cities across the world with its commitment to renewable energy, here's an example from that city's backyard -- The San Gorgonio Wilderness:

Wow. If we can clean up the air in our parks this dramatically in 20 years, maybe there's hope for getting Congress moving again, too. Send your representative a message supporting action on the dozens of wilderness protection bills that are still stuck in the system. 

This is about one of the big ones.

Tomorrow, I'll be in Los Angeles to watch as Mayor Antonio Villaraigosa officially announces that, within 12 years, the City of Angels will be entirely coal-free. Currently, L.A. gets almost 40 percent of its power from two old and notoriously dirty out-of-state coal plants -- the Navajo Generating Station in Arizona and the Intermountain Power Project in Utah.

It's impossible to overstate the significance of this announcement from the second-largest city in the U.S. But getting rid of coal is only part of the story. Los Angeles is also leading on clean energy.

Two years ago, L.A. was the first city in California to hit 20 percent clean energy. The city's new CLEAN LA Solar program (which allows local businesses, residents, and organizations to install renewable energy projects and sell the power they generate back to the utility) is the largest program of its kind in the nation. It's also expected to create 4,500 jobs and nearly $500 million in economic development for the city.

More jobs will be created as the city ramps up its already impressive energy-efficiency efforts. When the EPA released its annual ranking of cities with the most Energy Star certified buildings last week, Los Angeles topped the list -- as it has for the past five years.

Certainly, much of the credit goes to Mayor Villaraigosa. When he took office eight years ago, Los Angeles was getting almost half of its power from coal and only three percent from clean energy. When you fly  into LAX and see hundreds of square miles of rooftops soaking up the Southern California sun, it seems obvious that rooftop solar is a huge opportunity for L.A. But it took a mayor with vision and determination to make it happen.

I'm proud to stand by Mayor Villaraigosa as he announces a coal-free Los Angeles on Friday. You can join us -- the event will be live-streamed. In the meantime, let the sun shine!