The E-mail Commentary from Eco-Justice Ministries
Europe is just now emerging from an intense, week-long heat wave. The recent scorcher has been the most dramatic episode in a longer running drought and warm spell.
I've seen some tidbits in the news over the last week about records being set for all-time high temperatures in England, rapidly melting glaciers in Switzerland, and some early estimates about heat-related deaths.
But the largest story on that topic that I had noticed in the newspaper was one on "Modesty Melts in Steamy Paris." Few residences in the French capital have air conditioning, and it seems that a widely adopted response to the heat is to take off clothes, and to leave the curtains open. Ooh-la-la!
I do believe that the story about naked Parisians used up more column inches than the one about France's nuclear power plants threatening to overheat. In the face of a looming nuclear disaster, emergency permission has been given for the power plant managers to release hotter water from their cooling systems back into already warm rivers. Widespread fish kills are expected.
This morning's news upped the ante. We're way beyond fun human interest stories, and rather technical policy discussions. The French health ministry is now reporting that an estimated 3,000 people have died of heat-related causes in the last two weeks.
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So, is this European heat wave proof of global warming?
Let me guess what the meteorological experts are likely to say. Something along the lines of, "What we've seen in Europe is consistent with what we would expect under our best climate change models. But, no, this heat wave is not proof of global warming."
The problem is in what the experts call "variability." Local temperatures normally occur in quite a range. As you watch the weather report on TV, they'll almost always tell you about today's high and low temperatures, and they will point out how those compare with both average and record temperatures for the date.
If you keep track of weather data for 2 years, every day will set a "record" because there are no other pieces of information for comparison. After 50 or 100 years, most temperatures will fall somewhere between the records, although they will always fluctuate from a central average. But every now and then, the natural swing will still set a new record. So, setting a new high doesn't prove anything. It could be part of the natural variations.
One weather event -- even an extended one across a wide area like this year's European heat wave -- isn't an adequate basis for proving climate change. It might be an indicator, a factor, in a larger trend, but one event can't provide proof.
A stronger basis is found when the average daily temperatures from hundreds of sites around the world are combined in a computation of the average annual global temperature. Such a large batch of information is a better reflection of larger climate trends. The quirks of exceptional weather events even out. The weeks of extraordinarily hot weather in Europe may add a fraction of degree to the global average this year. But a span of cool weather somewhere else on the planet may cancel it out.
Even those annual averages have variability. For our whole planet, some years are a smidgen warmer or cooler than others. Just like the hot week in Europe is not proof, neither is a record high in the world-wide average proof of global warming. It might be an indicator, a factor, in a larger trend, but one exceptional year can't provide proof.
What the climate experts look at are trends in those annual average temperatures. In the 20th century, a multi-year average of the earth's temperature rose 0.7 degrees Celsius (about 1.25 degrees Fahrenheit). Most of that warming happened in the last decade of the century -- a period that set many record highs in the global average.
Statistically, the recent weather in Paris could be a fluke -- a rarity that only crops up a few times in a millenium. Statistically, the series of extra-warm years for the Earth that came along in the 1990s could be a fluke, too.
But when "flukes" start to happen most of the time, and when the pattern of those record-setting and average-distorting events is a pretty close match to the theory of what will happen when atmospheric concentrations of carbon dioxide go up and up, it becomes more and more likely that something has happened to the natural variability.
A strong pattern of rising average temperatures for the Earth adds to the probability that human factors are, indeed, changing the Earth's climate. Almost all of the experts now look at the evidence and see a high probability that human activities are warming the Earth's climate. Even those broad global figures don't provide proof. But it seems more and more likely.
And if that is the case, then what has happened in Paris looks like the sort of future we should all come to expect. The trend will be for higher-than-average and record-setting heat, year after year after year.
A few commentators have said that global warming would be a good thing. Others (including the Bush administration) have said that we shouldn't try to diminish global warming; we should adapt to the changes. The 3,000 people who have died from heat in France make those arguments hard to stomach.
This fall, the US Senate will vote on the Climate Stewardship Act, introduced by Senators McCain and Lieberman. Even though this summer's heat wave is not scientific proof, I hope that human and environmental tragedy in Europe can motivate us to lobby for sensible policies that will help to slow global warming.
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