TCS Daily


The Good News is the Bad News is Wrong

By Sallie Baliunas - November 22, 2001 12:00 AM

First, the good news. Petroleum, coal and natural gas supply around 84% of energy consumption in the U.S. and 80% worldwide. For now and the near future, fossil fuels are key to improving human health and welfare - and the environment. The reason is that energy use is essential to eradicating poverty that is destructive to humankind and the earth. We are grateful that longevity, human welfare and the environment have improved dramatically in the 20th century owing to unfettered access to energy.

Now, the (potentially) bad news: Fossil fuel use to supply energy has added carbon dioxide and other greenhouse gases to the air. Greenhouse gases in the air tend to retain some energy near the surface of the earth that would otherwise escape to space. As a result, the globally-averaged temperature near the surface of the earth should rise, perhaps considerably, in the absence of any quenching effects.

So is this bad news correct? Is human activity significantly warming the planet? To estimate the impact of the air's increased carbon dioxide content, scientists run computer simulations of climate, sometimes 100-200 years into the future. The outcomes of the computer models differ among the models. The middle-range estimate is around 2.5 C temperature rise by the year 2100, based on specific assumptions about energy use, population and the response of the climate to the bit of extra energy added by human-produced greenhouse gases in the air.

The models are complicated, reflecting the fact that climate itself is extremely complex. And a full simulation requires good knowledge of the relevant physical parameters and their interactions. Such a simulation requires knowing trillions of variables. But the computing capability does not yet even exist to run a full model, and knowledge of many of the physical processes required is lacking.

The natural greenhouse effect mainly arises from water vapor at altitudes above 1 to 2 miles, plus water droplets and ice crystals in clouds. Yet considerable uncertainty exists in those processes. It's true that all global climate models work with these uncertainties, and the calculations can continue in the absence of knowing the physical process. But checking the reliability of the calculations still poses an enormous hurdle.

It's as if the owner of a manufacturing facility wants to calculate its profit or loss. But the owner does not know two significant items: the cost of personnel, and the cost of operating the site. Still, the spreadsheet can be computed. But the outcome will have a bias - or systematic error in scientific phrasing - that contains major uncertainty.

No Substitute for the Scientific Method

One fashionable detour around the hard fact that water vapor and cloud processes are poorly understood is to average the outcomes of different simulations. But if each model misses the physics, then how reliable is the average of all the biased outcomes? Not much.

So be thankful for the scientific method, which insists that a prediction - such as the outcome of a computer simulation -- be checked against reliable measurements - such as changes in temperature and precipitation.

When we do that we find that the current computer simulations are exaggerating the globally-averaged warming that should have occurred in the last decades, if the models they use were correct.

According to the best measurements available, the response of the climate to the small amount of energy added by humans from increased carbon dioxide in the air has been small. This contradicts the model results.

For example, in the 20th century, the global average surface temperature rose about 0.5 C. At first glance the warming seems attributable to human fossil fuel use, which increased sharply in the 20th century. But the 20th century temperature shows three distinct trends: (1) strong warming of about 0.5 C beginning in the late 19th century and peaking around 1940; (2) a cooling from 1940 until the late 1970s; and (3) a modest warming trend from the late 1970s to the present, discounting the large natural warming pulse of the 1997-98 El Nino.

About 80% of the carbon dioxide from human activities entered the air after 1940. Note first that a substantial warming occurred early in the century, before 1940 - prior to the major buildup of the air's carbon dioxide concentration. After 1940, the surface temperature fell, and continued to fall through most of the 1970s. Since the late 1970s, surface temperature has risen. That means that the early 20th century warming must be largely natural, and that the human effects can be at most around 0.1 C per decade - the maximum amount of warming trend seen since the late 1970s.

And even that small recent global warming trend at the surface may not be attributable to human action. In the last decades, new technology space instruments have yielded critical information on the human effect on global climate change.

Computer simulations of climate also predict warming of both the surface the lowest layer of air - the lower troposphere (from roughly 5,000 to 28,000 feet). But the records from microwave sensors aboard satellites and validated independently by instruments carried aloft by balloons show that the large human-made warming trend predicted by computer simulations is absent. The lower troposphere satellite records are essentially global in coverage (unlike the surface record that extends, at best, over 20% of the surface of the earth), and precise. While there are multi-year increases and declines in temperature -- the strong El Nino warming pulse in 1997-1998, for example -- the human global warming trend of approximately 0.5 C forecast for the length of the record is not seen.

The record from balloons confirms the lack of a global warming trend from human activities. This record extends back to 1958, although with less dense spatial coverage than the record from satellites. According to that record, the lower troposphere shows a substantial warming in 1976-1977, owing to a natural, periodic shift in the Pacific Ocean that influences the global average temperature. But there is no significant global warming trend that could be attributed to humans before or after the Great Pacific Climate Shift of 1976-1977.

Looking at the best data and comparing them to the output of the computer simulations reveals that the simulations exaggerate warming. They exaggerate warming at the surface and, to a greater degree, warming in the lower troposphere. The computer results are also, presumably, exaggerating the forecasts of future warming.

And that's the good news from science for which we should be thankful. It means that the human effect on global warming is small and slow to develop. That allows time to continue to improve measurements and computer simulations of climate that will better define the magnitude of human-made warming. In turn, leaders can create a meaningful energy policy - one that is both effective and cost-efficient, while energy use continues to help feed and lift millions from suffering and poverty.

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