Today's New York Times features a story that may not shock you, but should concern us all:

According to internal reports dating back to 1995, scientists working for the Global Climate Coalition, an industry-sponsored group set up to wage a lobbying and public relations war against global warming action, were telling their bosses that human-caused global warming could not be refuted. But, that didn't stop industry lobbyists from waging a cynical campaign to undermine the science and cloud the debate.

Read the full story here.

Americans were outraged a decade ago when cigarette makers made similar claims about the evidence linking smoking and lung cancer. And then we discovered reams of damning research hidden away in tobacco company vaults.

The only real difference between then and now is that global warming stands to threaten more than just people — millions of species face extinction, entire ecosystems altered beyond recognition, the natural world as we know it today irreparably diminished.

This post is by Lisa Moore, Ph.D., a scientist in the Climate and Air program at Environmental Defense.

Scientists use some technical terms in discussing climate change that can cause confusion. Two that are especially useful to know are "forcing" and "feedback".

You'll hear these terms a lot in discussions of how human activity impacts climate - and especially when the topic turns to the melting Arctic. If you know what they mean, you'll have a much better understanding of the dynamics behind climate change.

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This post is by James Wang, Ph.D., a climate scientist at Environmental Defense.

You may have heard about the persistent droughts in the western U.S., Australia, and other regions. The Upper Colorado River Basin is experiencing a protracted, multi-year drought that started in 1999. Australia's record drought is threatening the livelihood of traditional farmers and ranchers.

At what point does a passing drought become a permanent shift to desert conditions, and why would such a thing happen?

It can happen because of global warming. Climate change can alter global winds, the strength and location of high and low pressure systems, and other climate factors.

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This post is by Sheryl Canter, an Online Writer and Editorial Manager at Environmental Defense.

When we first launched the Climate 411 blog, we posted a lot of useful articles on the basic science of climate change. I often want to link to them in other posts, but I have trouble finding them. If I have trouble finding them, you all certainly must, so here are the links, all in one place.

The Greenhouse Effect Explained
The Water Vapor Fallacy
Picturing a ton of CO2
Picturing 21 Million Barrels of Oil

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

Action Needed to Stop Global Warming
1. How Warm is Too Warm?
2. Worldwide Emissions Target
3. U.S. Emissions Target
4. Technologies to Get Us There

This post is by Lisa Moore, Ph.D., a scientist in the Climate and Air program at Environmental Defense.

A common refrain here on Climate411 is that we need to cut greenhouse gas emissions as soon as possible. One of the reasons we’ve cited numerous times is that, even if we could stabilize greenhouse gas concentrations at today’s levels, some global temperature increase is already locked into the system. This is sometimes called the "warming commitment" or the "warming in the pipeline".

What’s behind this phenomenon? The short answer is: water, water everywhere.

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This post is by James Wang, Ph.D., a climate scientist at Environmental Defense.

The wildfires in California prompted the largest mass evacuation in California history, destroying half a million acres and over 1500 homes. People are saying that global warming may have played a part in the severity of the blazes. But where is the connection? And how can global warming cause both floods and droughts?

Satellite photo of California wildfires. Source: NASA.

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The author of today's post, Bill Chameides, is Chief Scientist at Environmental Defense.

Last week we got a request to explain the Greenhouse Effect. Here goes.

Source: National Park Service, U.S. Department of the Interior

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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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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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This is the third 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

An argument I hear frequently from climate change skeptics goes like this: "Climate has undergone warming and cooling cycles for millennia. This is no different. It's just another naturally occurring warm cycle."

It's true that climate has undergone warming and cooling cycles for millennia, but it's not true that this is just another naturally occurring warm cycle. Here's why.

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