Climate Skeptic Case Wilts in Spring Heat and New Light
April 6, 2012
Reuters piece in Insurance Journal:
A clutch of recent studies reinforces evidence that people are causing climate change and suggests debate should now move on to a more precise understanding of its impact on humans.
The reports, published in various journals in recent weeks, add new detail to the theory of climate change and by implication cast contrarians in a more desperate light.
To be clear: there’s nothing wrong with doubting climate change; but doubts based on ignorance, a political bias or fossil fuel lobbying don’t help.
The basics, well known, are that rising greenhouse gas emissions are almost certainly responsible for raising global average surface temperatures (by about 0.17 degrees Celsius [app. 0.3°F] a decade from 1980-2010), in turn leading to sea level rise (of about 2.3 millimeters [0.0905 inches] a year from 2005-2010) and probably causing more frequent bouts of extreme heat waves and possibly more erratic rainfall.
Vast uncertainties remain about the risk of runaway warming, and the urgency: for example, about what level of greenhouse gas emissions will cause how much sea level rise this century.
The latest studies suggest firmer evidence for a human finger print, for example showing that pollution is largely responsible for a slow cycle in sea surface temperatures in the last century.
Recent studies also cast more light on trends, for example showing that the world has seen hotter years since 1998 (previously held by some as a record); and presenting firmer forecasts for 2050.
And others show lessons from the end of the last Ice Age: for example that rises in carbon dioxide preceded (and, by implication, caused) warming; and that sea levels at one point were rising by several meters a century.
None of these are individually particular clinchers – the problem was already clear – but collectively they pin down uncertainty seized on by skeptics.
Climate science was under a cloud after a “climategate” scandal of scientists’ emails leaked in 2009 was used by skeptics to suggest that they had deliberately manipulated data – allegations rejected by several public enquiries.
And a major U.N. panel report made a couple of factual errors, most notably saying that all Himalayan glaciers may melt by 2035, which seemed a typographical error meant to read 2350.
In retrospect, it’s incredible that these cast doubt on the scientific theory.
Rising levels of carbon dioxide drove much of the global warming that thawed Earth at the end of the last ice age.
That’s the conclusion a team of scientists has drawn in a new study examining the factors that closed the door on the last ice age, which ended about 20,000 years ago.
The result stands in contrast to previous studies that showed temperatures rising ahead of increases in atmospheric CO2 levels. This has led some skeptics of human-triggered global warming to argue that if warming temperatures came first, CO2 wasn’t an important factor then and so can’t be as significant a factor today as most climate scientists calculate it to be.
The measurements from the previous studies were taken from ice cores extracted from thick glaciers in Antarctica. The new work supplements that data with temperature evidence from 80 locations around the globe.
The results show that while temperature increases around Antarctica appear to have led increases in atmospheric CO2, the picture globally was the opposite – CO2 increases paved the way for temperature increases.
“The new work is a significant advance” in the study of the climate conditions surrounding Earth’s cycle of ice ages, notes Richard Alley, a Penn State University geologist who specializes in studying glaciers and the climate records encoded in the ice.
It’s the latest indication that researchers’ understanding of CO2’s effects on climate “is confirmed by the history of climate,” he writes in an e-mail.
He notes that during the 10,000 years from the end of the last ice age to the beginning of the current “interglacial” climate, atmospheric CO2 concentrations rose 40 percent, from 180 molecules per million in the atmosphere to 260 parts per million. During the past 100 years, concentrations have risen 34 percent, from 292 ppm to 392 ppm – and continue to rise.
“Clearly, it’s not a small amount,” says Dr. Shakun, referring to the increases during the past century. “Rising CO2 at the end of the last ice age had a huge effect on global climate. We’ve raised it as much in the last century.”
That doesn’t mean the full impact of these increases will appear during the course of this century, he explains. It takes much longer for the climate system to fully respond. The oceans are intercepting much of the current warming and additional CO2 humans have added to the atmosphere through burning fossil fuels and land-use changes. And Earth still hosts enormous ice sheets in Greenland and over Antarctica to keep things relatively cool.
“It will take many centuries and beyond to fully feel the effects,” Shakun says
There is not doubt that some in the denial movement will go to their graves faithfully reciting at least portions of the Fox News/Tea Party canon – that climate change is not real, that those WMDs are still out there, or that the earth is 6000 years old. But progress is real, and knowledge is cumulative. Even as Mother Nature is giving us harsher and clearer messages about the changes we have set in motion, continued research makes our choices even starker and more urgent.