Author Archives: Bill Chameides

What Has the Government's Climate Program Achieved?

Today's post is by Bill Chameides, Ph.D., science adviser to Environmental Defense and member of the National Academy of Sciences.

In 2002, the Bush Administration set up the Climate Change Science Program (CCSP). Yesterday, an independent panel released a report through the National Academy of Sciences (NAS) evaluating how that program has done. The headline in the New York Times sums it up: "Panel Faults Emphasis of U.S. Climate Program."

When I look at the work of the CCSP over the last five years, here's what stands out.

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Posted in News | 3 Responses, comments now closed

Extreme Weather Across Europe

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

A week or so ago I wrote about all the recent extreme weather in the United States. Well, it's not just happening here. Great Britain is being hit by the worst flooding in decades, and it keeps on raining. A heatwave blanketing south-eastern Europe has killed hundreds of people, and out-of-control wildfires are burning across Greece.

Is this global warming? It's impossible to say for sure what causes a particular weather event, but global warming does make extreme weather events more likely. Whether or not the events in Europe are due to global warming, I do think the Europeans are, unfortunately, getting a taste of things to come. For more, visit our Web page on global warming and extreme weather.

Posted in Extreme Weather | Comments closed

Gray's Hypothesis Doesn't Hold Water

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

This morning, the Wall Street Journal published an Op-Ed by Dr. William Gray titled "Hurricanes and Hot Air". In it, Dr. Gray argues that there is no link between global warming and the recent "increase in major hurricanes".

Unfortunately, this piece has several inaccuracies and omissions. Let me clear them up.

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Posted in News | 12 Responses, comments now closed

The Greenhouse Effect Explained

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.

The Greenhouse Effect

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

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Posted in Basic Science of Global Warming | 4 Responses, comments now closed

Short-term Change and El Niño

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

Last week in our Suggestion Box we got this question:

I've compiled a NCDC state by state average temperature map and trends from 1895 thru 2006. 1998 was the warmest year, but years since then are showing either the same as 1998 or cooler in most states. How can I explain to people why average temps haven't been warming EVERY year since 1998 instead of going up and down?

This is a good question, and one I get fairly often, so let me try to explain.

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Posted in News | 8 Responses, comments now closed

Extreme Weather: This Season's Norm?

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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Posted in Extreme Weather | 50 Responses, comments now closed

Part 5 of 5:  The Only Explanation Left

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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Posted in Basic Science of Global Warming | 22 Responses, comments now closed

Global Warming and the Ozone Hole

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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Posted in News | 4 Responses, comments now closed

Part 4 of 5: Medieval Warming Period

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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Posted in Basic Science of Global Warming | 12 Responses, comments now closed

Part 3 of 5: Causes of Past Climate Change

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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Posted in Basic Science of Global Warming | 19 Responses, comments now closed
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