May 10, 2005

Global Warming: Something New Under the Sun?

Filed under: Aerosols, Climate Forcings, Solar

That appears to be what is happening, judging from three papers in the May 6 issue of Science.

These three papers argue that the amount of incoming solar radiation reaching the surface of the earth has increased dramatically in the last two decades. While the values vary from paper to paper, in toto the new studies suggest that the increase in solar radiation absorbed at the earth’s surface had almost 10 times as much warming power during that time as the concurrent increases in carbon dioxide, the main global warming gas. Therefore, the warming observed over the past 20 years must have little to do with changes in greenhouse gases.

Before you kill the greenhouse effect, please note that we think this is a lot of hooey. But if you accept these results, that’s where you have to go.

You’d think it would be huge news that the greenhouse scare is over. Instead, the “news” sections of Science and Nature are behaving in their predictable fashion. In Nature, Quirin Schiermeier wrote “this may worsen the greenhouse effect.”

Really?

Changes in the sun or in the net amount of energy transmitted down to the surface are conveniently measured in watts per square meter (W/m2). For comparison, think of a 100 watt light. That does a pretty good job of warming the meter beneath it. While the changes in wattage from carbon dioxide or the sun are much less, they are changes nonetheless. Remember our recent piece on James Hansen’s recent calculations . He now feels that the change in temperature that ultimately results is two-thirds of a degree (C) per watt change (down from one degree that he used for years, thanks to the reluctance of the earth to warm as predicted). That should have been big news, too, and it was also entirely missed by Science, Nature and the press in general.

Here are the wattage changes reported in Science:

Enhanced greenhouse effect during industrial era: 2.4 W/m2. According to page 66 of the 2001 compendium of the United Nations’ Intergovernmental Panel on Climate change (IPCC), about a quarter of this amount, or 0.6 W/m2, has occurred since the mid-1980s.

Change in solar radiation absorbed by the earth from 2000 to 2004, estimated from low-orbiting satellite data, reported by Wielicki et al.: 2.06 W/m2.

Change from 1983 to 2001 in solar radiation absorbed by the earth, estimated at the surface by satellites, reported by Pinker et al.: 2.7 W/m2.

Change from 1985 to 2000 solar radiation absorbed at the surface, as measured at the surface, reported by Wild et al.: 4.4 W/m2.

If we average the results of Pinker et al. and Wild et al., we get 3.55 W/m2 for the period 1985 to 2000. To this we add 2.06 W/m2 from 2000 to 2004 and get 5.61 W/m2. If we divide this by 0.6 W/m2 (the total change in greenhouse forcing from 1985 to 2004, we get 9.35. The added forcing from increased solar radiation reaching the earth’s surface has contributed nearly 10 times as much energy as greenhouse changes! When compared to the overall greenhouse forcing since pre-industrial times, it’s four times larger.

(We converted the numbers above to watts per square meter from the values given in different units by Robert Charlson et al., in an accompanying “Perspectives” piece in the same issue of Science)

Further converting the numbers above to temperatures, we arrive at the following. The earth has been warming during the past 35 years at a very constant rate of about 0.18 ºC/decade. Traditionally, this has been associated with the overall response to greenhouse gas changes (remember, their radiation effect, since the industrial revolution, is 2.4 W/m2). If increases in solar radiation reaching the earth’s surface in the last 20 years are 10 times greater than that from carbon dioxide, and four times greater than the greenhouse gas changes in the last 150 years, which is more important?

Don’t forget that it accepted in climate science that the warming of the early 20th century, about 0.4˚C, is due largely to solar changes. In other words, it was pretty concurrent with the varying amount of radiation reaching the surface. So the recent changes in received solar energy should have exerted a tremendous influence on temperature!

Let’s be frank. This wildly fluctuating amount of solar radiation warming the surface invalidates every carbon-dioxide driven climate model for the past, as well as every future projection of warming resulting from greenhouse effect changes.

Why is the amount of solar radiation reaching the earth’s surface increasing? The authors of the Science papers don’t have a firm idea, but most tend to think that it has to do with the atmosphere becoming generally cleaner as a result of less pollution being emitted into it rather than actual changes in the solar output.

But regardless of the cause, if you believe all of this, then enhanced greenhouse gases are inconsequential compared to the tremendous increase in solar energy hitting the surface. Apparently few want to admit to this.

But some timid voices are beginning to whisper. NASA’s Bruce Wielicki, lead author of one of the new Science articles, told the New York Times on Friday, May 5th that the amount of increased energy coming from the sun matches the amount of energy that NASA’s James Hansen reported on Science’s web site just last week is being absorbed by the world’s oceans. What Wielicki failed to mention (or what the Times failed to report) was that Hansen ascribed to increases in ocean heat storage to the greenhouse effect!

It can’t be both. If it’s the sun, than greenhouse warming is dramatically overestimated. If it’s greenhouse warming, than the solar effect is an artifact of the research methods and nothing more.

So, either the three independent papers just published in Science magazine are wrong, or the earth’s sensitivity to changes in the greenhouse effect is exceedingly small.

Truth be told, something really stinks here. If the amount of solar energy hitting the globe as a whole fluctuates as wildly as these papers believe, then there’s a tremendous amount of stability built into the climate.

But the solar changes are almost certainly wild overestimates. For one thing, we have a pretty good test of how quickly the earth responds to much smaller changes in incoming radiation, as occurs when a big volcano blows off. The eruption of Mt. Pinatubo, in 1991, lowered the amount of incoming solar radiation by about 1.5 W/m2 and subsequently dropped the surface temperature about a half of a degree within two years. A clear cause and effect. The rises now purported in solar radiation are several times larger than that (as are the reported declines in solar radiation that preceded the recent rise). So their impacts should be obvious, instead of hiding in the fine print of a highfalutin science journal. In fact the earlier declines were of such magnitude that they should have completely disrupted the world’s food system, which obviously did not happen.

Obviously something is very wrong here. If the solar radiation received by the surface of the earth changed this much, earth’s surface temperature would be fluctuating wildly. Instead, the slow, modest and steady increase established 35 years ago continues, as predicted by mainstream computer models.

That’s our take, because it’s the only one that seems internally consistent. But, if somehow we are wrong (a rare event), then greenhouse warming is over, as the sensitivity of the earth’s temperature to carbon dioxide has been grossly overestimated. Believe us, we’d like to hope the latter is correct, but we have to call things in the most logical fashion.

References:

Charlson, R., et al., 2005. In search of balance. Science, 308, 806.

Hansen, J.E., et al., 2005. Earth’s energy imbalance: confirmation and implications. Sciencexpress, April 28, 2005.

Pinker, R.T., et al., 2005. Do satellites detect trends in surface solar radiation? Science, 308, 850-854.

Schiermeier, Q., 2005. Clear skies end global dimming. Nature, published on-line, May 5, 2005.

Wielicki, B., et al., 2005. Changes in Earth’s albedo measured by satellite. Science, 308, 825.

Wild, W., et al., 2005. From dimming to brightening: decadal changes in solar radiation at Earth’s surface. Science, 308, 847-850.




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