Four Reasons To Worry About Global Warming: Beyond Scientific Consensus

Yesterday I was struck by a Forbes headline, 97% Of Climate Scientists Agree Is 100%Wrong. The post questions the way Australian science popularizer John Cook arrived at this often-quoted number to illustrate the scientific consensus that human activity is contributing to global warming.

I agree with one statement in the post, which is the premise that in science, logic and explanation trump scientific opinion. I would have said logic and evidence, but thats close enough. And yet, the piece focuses primarily on the derivation of the 97% statistic, rather than on the logic and explanation behind the concern over human-generated global warming and the widespread fear among scientists that global warming will indeed prove dangerous and costly. I decided to expand on this post by giving some climate scientists a chance weigh in.

1: The oceans are getting warmer.

Measurements of global air temperatures show a long-term rise over recent decades, but the rise isnt steady. Like the stock market, it jumps up and down on shorter time scales. There was a spike in 1998, for example. If you measure global warming from that year onward, you get a distorted picture the overall trend, said Penn State climatologist Richard Alley. The trend over decades is what we should focus on.

Whats even more worrisome, he explained, is that air temperatures only give part of the picture. The real concern with the buildup of greenhouse gases is that were getting more energy from the sun than were sending back into space, he said. That energy, he said, is not only warming the atmosphere, its also melting ice and warming the oceans.

The oceans have warmed by about .3 degrees F since 1969, according to NASA. How much greenhouse gas-related heating goes into the ocean depends on currents known as El Nino and La Nina, he said. Those currents affect the surface temperatures of the oceans, with warmer water coming to the surface during the El Nino phase. In 1998, El Nino switched to La Nina. That shift caused cooler water to come to the surface and allowed the oceans to absorb heat like a big sponge.

During the years since, the measured air temperature rise has flattened. Some people have used that trend to argue that global warming has stopped. It hasnt. The currents have tended to oscillate, said Alley, so eventually the oceans will switch back to the El Nino pattern, after which that warmer water will come back to the surface and force more heat to go into the atmosphere.

2: Theres experimental evidence showing that carbon dioxide in the atmosphere acts to direct heat back toward Earth heat that would otherwise have been lost to space. Thats the greenhouse effect. And theres ample data showing that weve changed the composition of the atmosphere enough to alter the global climate.

In fact, human activity has nearly doubled our atmospheres load of carbon dioxide since the Industrial Revolution started. The basics behind this are the laws of physics, said Ben Horton a professor of marine and coastal sciences at Rutgers University.

The reason we accept that fossil fuel burning is increasing CO2 and warming the planet comes down to basic physics and chemistry thats more than 100 years old, said Penn State University climatologist Michael Mann. The fact that were measuring the effects is validation of the prediction.

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Four Reasons To Worry About Global Warming: Beyond Scientific Consensus