Global Warming Fact-Sheet

Posted by jns on 27 May 2007

Via NASA’s Earth Observatory mailing list my attention was drawn to their newly freshened Global Warming fact sheet, written by Holli Riebeek (dated 11 May 2007), and I wanted to take this space to draw more attention to it.

As most of my readers will know, there’s a great deal of misleading disinformation and obfuscation in our current global-warming “debate” here in the US, a concerted effort by some business and political forces to confuse the public into thinking that there is no scientific consensus on anthropogenic climate change, i.e., global warming because of carbon-dioxide (and other greenhouse gas) emissions being pumped into the atmosphere from human sources.

There is consensus among scientists working in the field; how and why and what it all means is nicely summarized in this short, succinct, and accurate fact sheet. Without being patronizing and without distorting the information, it’s a clear and understandable presentation of what we (the science “we”) know about global warming, the trends, the causes, and the likely or possible consequences.

In particular, the author addresses this question:

But why should we worry about a seemingly small increase in temperature? It turns out that the global average temperature is quite stable over long periods of time, and small changes in that temperature correspond to enormous changes in the environment.

It keeps popping up as a joke, especially during wintertime or a cool day in the summer, when people casually say “I wouldn’t mind a bit if it were a degree or two warmer”.

What is missing in this superficial understanding is a realization that, overall, the Earth’s temperatures are quite stable on average, and that very small changes in average temperatures can have very, very large effects on weather patterns and that those changes in weather patters lead to subsequently surprisingly large shifts in the weather we get at any particular location. In other contexts this is sometimes called “the butterfly effect”: consequences can be out of all proportion (i.e., nonlinear) to the causes. Ice ages have been accompanied by changes in the average global temperature of only about 5°C — which doesn’t sound all that big.

This is discussed quite well in the fact sheet, and summarized (in part) this way:

Potential Effects

The most obvious impact of global warming will be changes in both average and extreme temperature and precipitation, but warming will also enhance coastal erosion, lengthen the growing season, melt ice caps and glaciers, and alter the range of some infectious diseases, among other things.

For most places, global warming will result in more hot days and fewer cool days, with the greatest warming happening over land. Longer, more intense heat waves will become more frequent. High latitudes and generally wet places will tend to receive more rainfall, while tropical regions and generally dry places will probably receive less rain. Increases in rainfall will come in the form of bigger, wetter storms, rather than in the form of more rainy days. In between those larger storms will be longer periods of light or no rain, so the frequency of drought will increase. Hurricanes will likely increase in intensity due to warmer ocean surface temperatures.

It’s a good piece and a few minutes invested in reading through it will arm the reader with better understanding that will help cut a confident path through the thicket of opinions and misinformation that have clogged the information superhighway on the issue lately.