Later On

A blog written for those whose interests more or less match mine.

Thoughts on the science of global warming

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In another forum, I brought up global warming and submitted a little poll. I was surprised by the results:

What’s your take on global warming?
It’s not happening.
11% [ 6 ]
It’s happening, but totally due to natural causes outside our control.
39% [20]
It’s happening and it’s man-made and nothing we can do about it.
11% [ 6 ]
It’s happening and it’s man-made and if we take action, we can still correct the situation.
37% [19]
Total Votes : 51

11% still think there is no global warming, in spite of the dwindling Arctic icecap, the vanishing of glaciers, the melting of the Greenland ice cap, and the anomalous high temperatures over the entire globe. That surprised me, but then I remembered the old Army axiom: “10% never get the word.” No matter how thoroughly the word that “we’ll move out at dawn” is passed down the chain of command with orders that every troop be told, the next morning will find 10% taken totally by surprise by all the activity. So that accounts for that.

UPDATE: A little more insight into the 10%: a remark made by one who voted that it’s not happening pointed out that Greenland’s climate was once much warmer than it is today—the implication being that, if climate scientists knew this fact, they would not be saying that we experiencing global warming. Climate scientists, of course, know substantially more about the historical and pre-historical climate changes that most, and one is reminded of Alexander Pope’s point:

A little learning is a dangerous thing
Drink deep, or taste not the Pierian spring:
There shallow draughts intoxicate the brain,
And drinking largely sobers us again.

I might add that it was not until my sophomore year of college that I realized that “largely” modifies “drinking,” not “sobers”: it is drinking largely (as opposed to shallow draughts) that makes us sober once more.

But what about the 20% who imagine that it’s totally due to natural causes?

Some clarification came in comments: one person suggested that the amount of greenhouse gas issued by volcanoes, fumaroles, geysers, and the like was greater than the anthropogenic greenhouse gases by a factor of 3650: that is, those natural sources emitted “more in one day than mankind produces in ten years.” Since anthropogenic greenhouse gases are currently running about 26.7 billion tons a year of just CO2, that would put the output from volcanoes at around 97.5 trillion tons per year. In fact, the total of CO2 and SO2 emissions from the natural sources listed is around one-quarter of a billion tons—two orders of magnitude less than anthropogenic causes. (See here and here (pdf) for source articles.)

So part of it stems from simply not knowing the facts. But there was another interesting comment made by more than one: reference to the fear of global cooling raised in the early 70’s. So some of it is, as President Bush said, “There’s an old saying in Tennessee — I know it’s in Texas, probably in Tennessee — that says, fool me once, shame on — shame on you. Fool me — you can’t get fooled again.”

This position, I think, fails to take into account what’s happened in the 35 or so years since the early 70’s. Think about it for a minute: microcomputers (IBM’s microcomputer came out in 1981) and embedded microprocessors (the little embedded microcomputers that are now everywhere, from our autos to our kitchen appliances). Observation satellites and the Global Positioning System. The Internet. And a lot more knowledge about our planet and the climate. Indeed, we now have 35 more years of historical data from ice cores gathered from the Antarctic and the Greenland ice cap, so our understanding of the history of climate is much greater.

Science builds on a foundation of data. It takes the data that it now has to test its current theories and try out new ones—and it’s always, always gathering more data. We now can gather surface-temperature data by satellite, from oceans and land. We can release buoys, containing microcomputers and GPS systems and sensors, to float with the currents and transmit observations of temperature, salinity, wind speed, and the like. We can grind this data with much bigger computers—teraflops of processing power. Scientists can exchange data, theories, requests via the Internet—both person-to-person and in forums. And more and more of the data are digitized: computer-ready from the start. That’s how my dentist looks at my X-rays immediately and can retake them if needed, and get magnified views on the spot. (I was recently told of a radiologist who works from home in a tiny village in backwoods Pennsylvania, reading (digitized) X-rays from all over the country at home: digitized images, the Internet, and the radiologist is part of the hospital staff, as it were, at a vast collection of hospitals.)

35 years ago scientists did the best they could with the data they had, but they didn’t rest there (unlike Rumsfeld, who went to war with the Army he had and then did nothing to provide the equipment they so desperately needed). They invented new instruments, new ways to gather more data and new data, all digitized, and they had the processing (computer) power to manage the data and the communications (Internet) to share the data.

So some are stuck with memories of past approaches and capabilities and don’t understand how much things have changed, how much more is known about the world’s climate.

But still: when climate scientists worldwide come to a consensus agreement that we are experiencing global warming at an increasing rate, and it’s due to anthropogenic gases, how can their knowledge and observations and expertise be so readily dismissed? I don’t know. I suspect it’s something to do with a hunger for the status quo: a desire that things not change. But they do. And the scientists are trying to tell us that:

The Scientific Consensus on Climate Change
by Naomi Oreskes

Policy-makers and the media, particularly in the United States, frequently assert that climate science is highly uncertain. Some have used this as an argument against adopting strong measures to reduce greenhouse gas emissions. For example, while discussing a major U.S. Environmental Protection Agency report on the risks of climate change, then-EPA administrator Christine Whitman argued, “As [the report] went through review, there was less consensus on the science and conclusions on climate change” (1). Some corporations whose revenues might be adversely affected by controls on carbon dioxide emissions have also alleged major uncertainties in the science (2). Such statements suggest that there might be substantive disagreement in the scientific community about the reality of anthropogenic climate change. This is not the case.

The scientific consensus is clearly expressed in the reports of the Intergovernmental Panel on Climate Change (IPCC). Created in 1988 by the World Meteorological Organization and the United Nations Environmental Programme, IPCC’s purpose is to evaluate the state of climate science as a basis for informed policy action, primarily on the basis of peer-reviewed and published scientific literature (3). In its most recent assessment, IPCC states unequivocally that the consensus of scientific opinion is that Earth’s climate is being affected by human activities: “Human activities … are modifying the concentration of atmospheric constituents … that absorb or scatter radiant energy. … [M]ost of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations” [p. 21 in (4)].

IPCC is not alone in its conclusions. In recent years, all major scientific bodies in the United States whose members’ expertise bears directly on the matter have issued similar statements. For example, the National Academy of Sciences report, Climate Change Science: An Analysis of Some Key Questions, begins: “Greenhouse gases are accumulating in Earth’s atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise” [p. 1 in (5)]. The report explicitly asks whether the IPCC assessment is a fair summary of professional scientific thinking, and answers yes: “The IPCC’s conclusion that most of the observed warming of the last 50 years is likely to have been due to the increase in greenhouse gas concentrations accurately reflects the current thinking of the scientific community on this issue” [p. 3 in (5)].

Others agree. The American Meteorological Society (6), the American Geophysical Union (7), and the American Association for the Advancement of Science (AAAS) all have issued statements in recent years concluding that the evidence for human modification of climate is compelling (8).

The drafting of such reports and statements involves many opportunities for comment, criticism, and revision, and it is not likely that they would diverge greatly from the opinions of the societies’ members. Nevertheless, they might downplay legitimate dissenting opinions. That hypothesis was tested by analyzing 928 abstracts, published in refereed scientific journals between 1993 and 2003, and listed in the ISI database with the keywords “climate change” (9).

The 928 papers were divided into six categories: explicit endorsement of the consensus position, evaluation of impacts, mitigation proposals, methods, paleoclimate analysis, and rejection of the consensus position. Of all the papers, 75% fell into the first three categories, either explicitly or implicitly accepting the consensus view; 25% dealt with methods or paleoclimate, taking no position on current anthropogenic climate change. Remarkably, none of the papers disagreed with the consensus position.

Admittedly, authors evaluating impacts, developing methods, or studying paleoclimatic change might believe that current climate change is natural. However, none of these papers argued that point.

This analysis shows that scientists publishing in the peer-reviewed literature agree with IPCC, the National Academy of Sciences, and the public statements of their professional societies. Politicians, economists, journalists, and others may have the impression of confusion, disagreement, or discord among climate scientists, but that impression is incorrect.

The scientific consensus might, of course, be wrong. If the history of science teaches anything, it is humility, and no one can be faulted for failing to act on what is not known. But our grandchildren will surely blame us if they find that we understood the reality of anthropogenic climate change and failed to do anything about it.

Many details about climate interactions are not well understood, and there are ample grounds for continued research to provide a better basis for understanding climate dynamics. The question of what to do about climate change is also still open. But there is a scientific consensus on the reality of anthropogenic climate change. Climate scientists have repeatedly tried to make this clear. It is time for the rest of us to listen.

Written by Leisureguy

26 February 2007 at 10:38 am

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