A Dartmouth College professor says a 1 year study has raised key questions about the significance, mechanics, and timing of global warming and its causes.
Robert Jastrow urged a 5 year deferral of policy decisions on carbon emissions and other fossil fuels burning.
Such a delay would allow little further harm and give scientists time to conduct research needed to give policy makers and the energy industry the facts needed for sound decisions, he told the American Petroleum Institute's annual meeting last week.
DEALING WITH WARMING
Jastrow, adjunct professor of earth sciences at Dartmouth since 1974, said so many scientists are focused on the greenhouse situation it seems very likely significant progress will be made in 3-5 years.
The policymaking delay would be wise because a study by George C. Marshall Institute scientists has raised many questions about the theoretical estimates that have led to alarm about the greenhouse threat.
Earth's temperature has risen 0.5 C. in the last 100 years, coinciding with a large observed increase in the volume of carbon dioxide and other greenhouse gases in the atmosphere. The gases apparently result from burning of coal, oil, and gas.
National Aeronautics and Space Administration estimates of the temperature increase that should have occurred based on the observed higher greenhouse gas content agree roughly with the theoretical estimates.
That agreement implies that "we should pay attention to what the calculations predict for the next century," but the predictions yielded by the greenhouse theory appear to fail the test of comparison with observation in nearly every important respect.
GREENHOUSE DOUBTS
Questions raised include:
- Most of the greenhouse gases were emitted into the atmosphere after 1940, but nearly all the observed temperature increase occurred before 1940. Therefore, other factors must have caused part-possibly a large part-of the warming.
- After 1940, earth temperatures cooled for 30 years, during which greenhouse gases built up rapidly in the atmosphere, then started to rise in the 1970s. Scientists disagree over the size of greenhouse warming but all agree it cannot cause a cooling.
- Precise satellite measurements of global temperatures that became available last year show no significant temperature change for the 1980s, while theoretical estimates show a small but significant rise of 0.2 C.
- Computations show the Northern Hemisphere should have warmed 0.5 C. more than the Southern Hemisphere, but observations reveal no difference.
- All computations predict high latitude warming at twice the global average, but observations show high latitude warming is smaller and tropical latitude warming nonexistent, the reverse of the computational prediction.
Jastrow points out that a single computation of simulated climate requires about 20 equations. It contains dozens of constants whose values are crucial but often have to be estimated.
The computer program takes tens of thousands of lines of code, and a single computation of 100 years of simulated climate takes about 10 quadrillion bits of arithmetic.
IMPLICATIONS
The questions show there is good reason to believe that the true greenhouse warming in the last 100 years was different from 0.5 C.
"It could be less or it could be more, depending on whether those factors added to or subtracted from the greenhouse warming," Jastrow said.
Adjusted to allow for observational uncertainties, the projected temperature rise during the next 100 years would amount to 0.2 1.8 C., with a midpoint of 1 C.
The lower estimate would not significantly alter human affairs. The higher one might or might not be significant in the sense of requiring governmental constraints on greenhouse gas emissions.
Jastrow said, "Clearly, the uncertainty must be reduced if scientists are to give useful information to policymakers and the energy sector."
Calculations show that the most that can happen from a 5 year policymaking delay is an additional 0.1 C. warming in the 21st century.
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