With all that's going on in the world, it's easy to miss weather events. So you may not have noticed that U.S. weather patterns the last few months have been quite extreme and worrying.

From NOAA's National Climatic Data Center

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What is needed now is a strong, sustained, and well-coordinated effort between governments at all levels, businesses, civic institutions, and individuals to adopt policies, programs, and practices that accelerate the adoption of clean, efficient energy choices. The costs of delay are high. For every year of delay in beginning significant emissions reductions, global concentrations of heat-trapping gases rise higher and the goal of avoiding dangerous climate change becomes more difficult and more costly to achieve.

From Confronting Climate Change in the U.S. Northeast [PDF 8MB], prepared by the Northeast Climate Impacts Assessment Synthesis Team. July 2007.

For more on the toll of global warming in the Northeast, visit our New York City page.

This is the final installment of a five-part series by Bill Chameides on How We Know Humans Cause Global Warming.

1. A 175-year-old Puzzle
2. What Chemistry Tells Us
3. Causes of Past Climate Change
4. The Medieval Warming Period
5. The Only Explanation Left

Compared to 100 years ago, the temperature of the atmosphere is warmer. No one disputes that. And no one disputes that an extra source of heat must be causing it - that's a basic law of physics. But how do we know that the source of the heat is increasing levels of greenhouse gases from burning fossil fuels and deforestation?

So far in this series I've described how the relationship between atmospheric carbon dioxide (CO₂) and global warming was discovered, how carbon isotopes prove that rising CO₂ concentrations are from the burning of fossil fuels, and how the orbital shifts that cause ice ages cannot explain our recent warming.

That certainly suggests that global warming is caused by increased CO₂ from burning fossil fuels, but how can we be sure?

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The author of today's post, Lisa Moore, is a scientist in the Climate and Air Program.

In March of this year, British TV Channel 4 aired a 72-minute diatribe called "The Great Global Warming Swindle". The program is filled with old data, data taken out of context, data misattributed, and general misinformation, and at the time it aired we thought it not worth responding to.

But people keep mentioning it, so here are the program's main arguments and why they're wrong. Now the next time someone brings this up, you'll have the facts to give them.

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The author of today's post, Jeffery Greenblatt, Ph.D., is an expert on low-carbon energy technologies at Environmental Defense.

The U.S. may be short on oil and gas reserves, but the one energy source we thought we had in abundance was coal - enough to last 250 years at current consumption levels. Or so we thought.

A few weeks ago, the National Academy of Sciences (NAS) released a new report saying that U.S. coal reserves may last only another 100 years, or even less. That's a big difference. How did we get this so wrong, and what are the implications for U.S. energy policy going forward?

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Many people have asked me whether global warming and the ozone hole are related. The short answer is "no". The long answer starts with "tangentially". Here's the scoop.

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The author of today's post, Lisa Moore, is a scientist in the Climate and Air Program.

This week's scientific journals brought three interesting stories about climate change. The first is a sneak peek at an upcoming paper about global warming and the Sun. The second talks about an unexpected environmental benefit of hurricanes, and the third reports that climate change is drying up important biodiversity hotspots in the Arctic.

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Tomorrow's Live Earth concert is expected to be quite the happening. Do you think it will help the fight against climate change? Are you planning to go? If you do go, post your experiences here!

This is the fourth installment of a five-part series by Bill Chameides on How We Know Humans Cause Global Warming.

1. A 175-year-old Puzzle
2. What Chemistry Tells Us
3. Causes of Past Climate Change
4. The Medieval Warming Period
5. The Only Explanation Left

In my previous article in this series, I talked about climate change patterns over geologic time. I showed how today's spike in temperature and carbon dioxide (CO₂) concentration breaks patterns and records going back 600,000 years.

This departure can be seen even more clearly when you look at just the last 1000 years (see graph in previous post). So what is this you hear about a Medieval Warming Period?

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Today's post is from Sam Parry, Environmental Defense's manager of online membership.

As we prepare for July 4th festivities, I wanted to share an inspiring conversation we've had with our online supporters over the past several weeks. We asked the question, how do people who love this country approach the crisis of global warming? We must have struck a nerve because we got thousands of passionate responses.

We used these responses to craft a Declaration of New Patriotism. To date, almost 56,000 people have added their "John Hancock." Last week, we delivered the message to Congress with an ad in Roll Call, one of the most widely read newspapers on Capitol Hill.

So before you head out to celebrate tomorrow, take a look at our Declaration of New Patriotism and add your signature. Happy Fourth of July!