Green Week: Science of Climate Change

Andrew Freedman
Blogger, Capital Weather Gang
Wednesday, April 22, 2009 11:00 AM

It's easy on a warm day in the middle of winter to blame "global warming," but often that's not the case. So what is the latest evidence that shows our climate is changing?

Andrew Freedman, who writes about climate change for the Capital Weather Gang, discussed at 11 a.m. ET on April 22 the latest science discoveries and the difference between weather patterns and climate change.

Andrew Freedman is an environmental journalist with a lifelong fascination with the weather. His work has appeared on The Weather Channel's "Forecast Earth" Web site, in Congressional Quarterly, Greenwire and Environment and Energy Daily, as well as Weatherwise magazine. He is currently attending the Fletcher School of Law and Diplomacy at Tufts University as part of a dual master's degree program in climate change policy with Columbia University.


Hermosa, S.D.: In all my reading on climate change, I haven't seen a discussion of this ultimate question: could an increase in greenhouse gas ultimately make our planet unlivable, perhaps because earth's atmosphere changes to an extent that it no longer supports life?

And one stupid question: does greenhouse gas increase the intensity of sunlight? Sometimes I'm outside and think the sun just feels hotter than it used to, as if it's magnified by the atmosphere.


Andrew Freedman: Hi Michael,

I have actually heard a few experts discuss that question, but few people if any think that such an extreme outcome is likely to take place. Instead, the main concern is that climate change will make it hard for the world's current patterns of development and increasing population to be sustained. For example, sea level rise could threaten highly populated coastal areas, putting major cities at risk of flooding. Also, changes in precipitation patterns and weather and climate extremes could alter the areas that are suitable for growing food.

Climate scientists generally don't see climate change as something akin to a disaster movie (i.e. "The Day After Tomorrow"), but rather as a significant factor that will help shape how and where we live in the future.

As for the intensity of sunlight, I am not aware of any info that suggests that greenhouse gases increase the intensity of sunlight. Perhaps thinking about global warming on warm days makes it seem hotter?


Hutchinson, Kan.: How can anyone with basic intelligence believe that a gas that comprises less than 0.04 percent of the atmosphere can have any impact on atmospheric temperature? Why do people believe that trapping infrared radiation can heat the atmosphere when physicist R.W. Wood proved in 1909 that trapping IR did not cause heating in greenhouses or the atmosphere? Why are journalists ignoring the statements of astrophysicists that the current shortage of sunspots indicates the sun has entered the type of quiet period that occurs every few centuries - like the period in the 18th Century?

Andrew Freedman: Numerous studies have shown that trapping infrared radiation in the earth's atmosphere can and does affect the earth's temperature. If it didn't, we wouldn't enjoy the relatively balmy temperatures that we do, since the natural greenhouse effect helps keep the earth's average temperature much warmer than it otherwise would be.

I don't think journalists are ignoring astrophysicists, but the issue is that climate scientists have reported that solar cycles are not the main cause of recent climate change. They are a factor, and may help explain why the past couple of years have not been quite as warm as other recent years, but they don't explain most climate trends to date.


Freising, Germany: I've read that the North and South Poles are warming up quicker than the rest of the planet. Is there a scientific explanation for this?

Andrew Freedman: Hi Freising. Yes, it is true that climate change is taking place faster and is also more amplified at the poles, particularly in the Arctic, where most areas are warming at about twice the rate of lower latitudes. Antarctica is a more complicated picture, since some parts of the continent are cooling, and some parts are warming fast.

There are several reasons why climate change takes place more rapidly at the poles. A main reason for rapid climate change in the Arctic is because normally, that region is covered by sea ice which reflects a lot of incoming sunlight and helps keep the climate cool. When you melt that ice, more of the sun's energy is absorbed by the darker open water that replaces it, and this helps to heat the water and the atmosphere.

There are other factors at work too, but they are a bit more complicated to explain here. For a really in depth explanation, check out:


District of Columbia: Climate change models, to a degree, are based upon assumptions that aren't yet verified -- such as cloud feedbacks. How much will temperatures increase, or not, as more water vapor enters the atmosphere in a warmer world, and more clouds (probably) form, at different places and altitudes? The lack of definitive information about temperature feedbacks is one reason the IPCC forecast temperature range is so wide. If CO2 doubled, but everything else remained the same, there would be an increase of just one degree; and there seems to be something close to unanimity on this. One degree is not a big deal, again with large amounts of consensus. So how do we validate the sum of feedback?

We may have an opportunity in the next few years to judge the strength of solar warming and cooling, as the sun (according to NASA) is at the coolest level ever seen in the instrument era, going back 50 years (very low sunspot counts for almost two years, with 2008 the second lowest in 100 years, and very low solar wind, for example). Solar induced warming and GHG/black carbon warming together can only add up to a given temperature increase. The greater the effect of one, the less the effect of the other. So what would we say about the strength of GHG/black carbon, if the earth cooled by several tenths of a degree in the next few years (very much precedented in history, in the Dalton and Maunder minima)? If the sun has the power to cool the earth when it isn't very active, it would have the power to warm the sun when it is active, and it has been very active the last 50 years, again according to NASA.

Shouldn't we wait a few years to validate with real world data whether GHGs/black carbon have the feedback effects assumed but not validated in the climate change models, before establishing a legally binding scheme that, from history, won't be eliminated once enacted? Given the costs to the economy and the poor, wouldn't such a course be the most responsible one for all of us? What have we got to lose? If temps go up instead of down when the sun is weaker, it would prove to all but the most die hard skeptics that the GHG/black carbon scenario for warming is the right one. But if the opposite occurs, we will have saved ourselves huge amounts of money and economic growth, the impacts of which will, as always, be felt most at the bottom of the pile.

Andrew Freedman: Climate computer models are based largely on physical science - what scientists know about how the climate system works. There are a lot of factors that go into them, and some of them have more uncertainties than others. Cloud feedbacks, which you mentioned, are a key remaining uncertainty, since scientists say that how clouds change in a warming world may affect the pattern and extent of future temperature change. However, most studies show that cloud feedbacks are not likely to prevent most warming in the future, but that they may change where warming takes place or how much warming there will be.

Whether we wait another few years for more data, or listen to most climate scientists who say that reducing greenhouse gas emissions is necessary to prevent significant climate change, is in large part a policy decision that I won't weigh in on here. But a key point is that climate change will also involve significant costs, and will affect poorer nations more than comparatively wealthy ones like the United States.


Fairfax, Va.: Did you see John Boehner's interview on This Week? I found it to be almost comical. But I think he does have a point that if the U.S. moves ahead with a cap and trade program to limit emissions without getting the rest of the industrialized world to follow suit, we're creating a big risk for our economic growth, no?

Andrew Freedman: Hi, thanks for your question. I didn't see Congressman Boehner's interview on ABC News, but I have heard many others make that point about the potential costs of programs to reduce greenhouse gas emissions. On the Capital Weather Gang blog, we cover the science of climate change (in addition to our weather coverage), and not policy issues, so I don't want to weigh in on the merits and drawbacks of a particular climate change policy. I'll leave that to other Washington Post reporters.

However, in general I can say that because greenhouse gas emissions affect the entire globe, most climate scientists and policy experts agree that a truly international solution is needed to address the problem. In other words, the climate system doesn't care whether a molecule of carbon dioxide comes from a power plant in Virginia or China, since the effects from that molecule on the climate will be the same.

Needless to say, negotiators of the next climate change treaty have a difficult task ahead of them in trying to carve out an agreement between industrialized countries and developing nations.


Colorado: Hi,

I'm wondering if you have an opinion on why global warming science (as opposed to policy) has become so politically charged here in the U.S. as opposed to Europe. Do you think the U.S. press has somehow affected or perception of the quality of the science? Thanks.

Andrew Freedman: Hi Colorado, that's an excellent question.

Indeed, studies have shown that the U.S. media has portrayed climate science differently than the press in some European countries, such as the U.K. In the U.S., scholars report that the media has paid more attention to the so-called climate change "skeptics" who argue that climate change is not man made and/or is not a major problem. In Europe, such skeptics have not been cited as frequently or as prominently, particularly in the past several years. There are many possible reasons for this, mainly having to do with the different media cultures and practices in different countries, as well as different political systems.

I think the U.S. press affects the perception of climate science, and continues to do so through its climate science coverage. In general though, I think the main message the media is conveying these days is that climate change is a significant problem to be addressed, and that this reflects what most climate scientists are telling journalists such as myself.


Evanston, Ill.: As we have all seen in the last two years, economic modeling and forecasting is a highly inexact science. Given how complex modeling the climate is and how much less time and energy has been devoted to such measures, shouldn't we admit how inadequate so-called climate models are? Have any of these models successfully predicted anything? If so, what?

Andrew Freedman: Hi Evanston, I hope conditions are finally warming up there after a long and tough winter! (I used to live in Chicago and know how brutal it can be).

Your question is a good one, and is something that is on the minds of many readers, judging from the number of comments we get on the Capital Weather Gang blog. In general, climate scientists will be the first to admit that computer modeling is not an exact science. The climate system is extremely complex, and it is difficult to model it precisely. However, climate scientists who use computer models aren't really trying to get every last detail right and come up with a forecast for a particular day far into the future, or even a particular month or year.

Rather, what they are trying to do is determine the general trends that are likely to take place in response to emissions of greenhouse gases and different natural sources of climate change. Many of the models that climate scientists rely on to help show how the climate system may evolve in the future have accurately simulated the climate of the past several decades, which indicates that they have the ability to simulate real world climate trends.


Gainesville, Fla.: Please include in your presentation of climate change the geologic perspective. We are just out of the Little Ice Age, the climate is warming. Please explain how this has happened before. Talk about the 400 years or so of the Medieval warming period followed by the Little Ice age. The Vikings and the Islandic Sagas certainly document the first, and events in Europe certainly document the second. Any discussion of climate change/global warming HAS to include what we know of the geologic record.

Andrew Freedman: Thanks for your question. As you say, it is indeed important to keep in mind that the earth's climate has always been fluctuating from one phase to the next, oftentimes with violent and sudden shifts. Climate scientists use many different methods to try to put the climate change that has been happening recently into the proper geological context, and they have so far found that the changes happening today are extremely unusual and are likely related to human activities.

Geologists and climate scientists who peer deep into history by using what are called "proxy" records of past climate, such as ancient air bubbles trapped in glaciers, have a lot to teach us about how modern climate change compares to the swings that have occurred before.


Burke, Va.: Hello, for decades the coal industry has passed the cost of its products onto state's health and environmental resources. Regardless of what other countries do, do you feel that it's in our best interest to cap carbon pollution in order to spur new investments in domestic renewable energy, revitalize our manufacturing sector and create American jobs that can't be outsourced? How much do we pollute, man for man, compared to China and India?

Andrew Freedman: Hi, thanks for your question. I cover climate science for Capital Weather Gang, so I don't want to overstep my role by commenting on whether we should cap carbon pollution. On your question of how the emissions of an average American compare to an average citizen of China or India, the figures are quite humbling.

Americans emit the most greenhouse gases per person in the world. According to the World Resources Institute, an environmental think tank, in 2004 the average American emitted 19.84 metric tons of CO2. The average Chinese citizen emitted 4.23 metric tons, and the average Indian citizen emitted just 1.07 metric tons.


Reston, Va.: Is LandSat and SeaSat data used?

Do other nations have similar satellite systems?

In a global context, do universities who research climate change share data? Is there a general consensus on trends?

Andrew Freedman: Hi Reston, thanks for your question. In general, satellites are relied on more for weather monitoring and forecasting than for climate change information, although some satellites do provide data on climate trends. Several nations have environmental satellites that are in orbit, including the European Union and Japan.

Yes, universities do share climate change research, as does the U.S. government and other governments around the world. There is a general consensus on climate trends, which is expressed by the U.N. Intergovernmental Panel on Climate Change (IPCC). In its most recent report in 2007, the IPCC reported that the earth's climate had warmed by a little more than one degree Fahrenheit in the past century (.74 deg C), and that further warming is expected to occur over the next several decades.


Andrew Freedman: We're out of time for today, I am sorry I couldn't get to every question. Please stay tuned to Capital Weather Gang ( for ongoing climate science coverage each week, and especially for our unparalleled coverage of Washington Metro area weather. Enjoy your Earth Day!


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