Page images
PDF
EPUB

Predictability of Climate Change

Q12. Are there theoretical limits on the predictability of global climate? Please discuss.

A12. We do not know yet because the modellers have not focused on this. Answering this very important question is a major goal for a new program we have begun at MIT called the "Climate Modelling Initiative." Limits to predictability can come from chaos, poor models, and insufficient observations to determine initial conditions for models. When small adjustments to initial conditions, which are allowed due to the observational inadequacies, lead to very different predictions, that is an example of chaos. For example, chaos limits short-term weather predictions to being accurate, at best, for only a few to ten days into the future.

Climate Data and Observations

Q13. The 1995 IPCC report, The Science of Climate Change, concludes that, on a global average, the atmospheric temperature has risen by 0.3°C to 0.6°C since the late 19th century. Please discuss quality of the data record upon which this estimate was based. Is this record reliable and does it provide adequate global coverage?

A13. These estimates probably represent the best that can be done given significant inadequacies in global coverage, accuracy of instruments, reliability of observers, and needed corrections to account for local warming around observing stations due to urbanization. The uncertainties are larger than stated, but it would be quite improbable that the record is so bad that the world actually cooled over this time period.

Satellite Temperature Data vs. Surface Measurements

Q14. There has been a lot of controversy over the difference in the ground-based temperature record and the satellite/balloon record. Please provide for the record your views on this issue.

A14. Both observing systems have their strengths and weaknesses. Satellites provide global coverage but the deduced temperatures are less accurate than those obtained on site. Also each system is actually recording different things: for the on-site measurement it is the temperature in a thin layer of air at the surface, while for the satellites it is the surface temperature or the average temperature of thick layers of air. Given this difference and the uncertainties inherent in each system, we do not expect them to agree exactly.

IPCC Process

Q15. Dr. Spencer testified that “when the IPCC comes out and says, ‘2,500 scientist have agreed, now, that humans are responsible for climate change,' most of the scientists --besides that fact [of] not really being consulted on whether they agreed with that statement-most of them aren't even in a position to have a feeling for whether the big picture supports global warming or not." Do you agree with that statement?

A15. Yes, I agree very strongly.

Q16. You state that the IPCC process is not structured to provide the "required continuous up-to-date integrated assessment mechanism for policy." What do you think has to be changes to make the IPCC more responsive?

A16. The IPCC does not do research. It appoints teams of people of varying backgrounds, perspectives, and capabilities to review ongoing research, and in a limited way it influences research directions (if you say in your funding proposal that the IPCC says this is important, then it can carry weight). However, what is really needed for policy advice are teams of people working together to do the multidisciplinary research on integrated assessment on a continuous basis. I do not see how the IPCC can do this task at all. The IPCC could of course (and perhaps should) review and evaluate the research in integrated assessment every few years, just as it has done for the more narrowly focused disciplinary work in the past.

Impact of Industrial Country Emissions on Climate

Q17. A just-released IPCC study, Implications of Proposed CO, Emissions Limitations, found that, under the one proposal examined in detail (the Netherlands 2% proposal), the reduction in the global temperature increase in 2100 was estimated to range from 0.1°C to 0.9°C. Is this a reasonable estimate in your view?

A17.

I do not presently have a copy of this report, so I cannot comment. Q18. Bert Bolin, former Chairman of the IPCC, recently said that “ ... no reasonable future reduction in Annex I countries would stabilize global emissions." Do you agree?

A18. In general, I agree. Our own (MIT) study shows for example, that Annex I countries would need to have negative emissions by the middle of the next century in order to stabilize global emissions enough to prevent carbon dioxide levels from rising above 550 ppm. In other words, Annex I countries would need to be removing, not adding, this gas

"Little Ice Age” and Climate Models

Q19. From about 1550 to 1850, the world experienced the “Little Ice Age."

Q19.1. How do climate models incorporate the emergence of the globe from this climatic period?

A19.1. There is no accepted mechanism for either producing or coming out of the "little ice age." Possibilities include changes in the deep ocean (thermohaline) circulation and changes in solar output.

Q19.2. Are current GCMs able to reproduce this period?

A19.2. Given the uncertainties, and the capability for “tuning” climate models, I suppose these models could "reproduce the little ice age", but it would be contrived.

Melting of Glaciers in Glacier National Park

Q20. Can the melting of glaciers in Glacier National Park be attributed to global warming or were these glaciers been in recession before the increase in atmospheric concentrations of CO2 resulting from human activity?

A20.

This is a question whose answer requires accurate predictive capability for regional climate. We do not yet have that capability.

Hurricane Frequency

Q21. A paper co-authored by C.W. Landsea that appeared in the journal Geophysical Research Letters in 1996 shows that there has been a downward trend in the intensity of hurricanes since 1944. Another paper co-authored by Tom Karl also shows that since the 1940s the number of hurricanes making landfall in the U.S. also has declined. Is it fair to say, based on this peer-reviewed research, that the intensity and frequency of hurricanes have gone down in the last 50 years?

A21. I am not familiar enough with these data to comment, other than to say that I have no reason to disbelieve the conclusions from the two papers.

Hurricanes and GCMs

Q22. Many scientists have linked increasing temperatures with increased tropical storm activity, others have reached different conclusions. For example, a study by Robert Balling and others, which appeared in Meteorology and Atmospheric Physics in 1990, concluded that “There is basically no trend of any sort in the number of hurricanes experienced... with respect to variations in temperature." Looking to the future, Lennart Bengtsson of the Max Planck Institute of Meteorology reported in the journal Tellus that, based on model simulations, a doubling of CO2 would lead to fewer hurricanes. In your view, can a valid scientific case be made that an increase in CO2 could lead to no change or even a lessening of tropical storms?

A22. Current climate models totally fail to simulate hurricanes so I think the answer here must await further research.

Global Warming and the Possibility of a New Ice Age

Q23. Some researchers have recently projected that global warming could lead to a new ice age.

Q23.1. Do you lend this projection any credence, and if so why?

A23.1. Slowing of the deep ocean (thermohaline) circulation as a result of global warming is predicted in some models. This could cause significant cooling of the high latitudes which could then lead to increased snowfall, less evaporation of snow, and thus glaciation. But all of this is very speculative given the current inadequacies in both theory and modelling.

Q23.2. Do current climate models provide any guidance of this matter? If so, what do they forecast, and if not, does this mean that there will be no more ice ages?

A23.2. Current models imply we should study this issue much further in order to verify or reject the possibility for new ice ages. They do not provide reliable forecasts of such events.

Temperature and CO, Record

Q24. The geologic record reveals that major changes in the atmospheric concentration of CO2 and temperatures have occurred during the earth's history. Over the last 160,000 years the Earth's average temperature has varied by as much as about 14° F, while CO2 has varied from as low as about 160 parts per million to today's figure of more than 360 parts per million. While a general correlation of CO2 and temperature seems evident in this record, a closer examination reveals a number of contradictions. For example, about 135,000 years ago, when the temperature was some 3 degrees warmer than present, atmospheric CO2 concentrations were about 20 percent less than today. In addition, over the next 20,000 years, the temperature decreased by about 14 degrees, while the CO2 levels remained high and relatively constant during that period. More recently, in the interval between about 5,000 to 9,000 years ago, there were several short-lived warm periods when temperatures exceeded current levels by 1 to 2 degrees, but CO2 levels were about 25 percent below today's levels. The greenhouse theory tells us that we should expect more warming when there is more CO2 and less warming or even cooling when there is less CO2, but it appears that none of these features of past climate can be explained by the greenhouse theory.

Q24.1. Given the above, is it true that for millennia, there has been a clear correlation between CO2 levels and the global temperature record.?

A24.1. In the millennia since the last ice age the answer is no.

Q24.2. Given the above, is it true that records of past climate going back as far as 160,000 years indicate a close correlation between the concentration of greenhouse gases in the atmosphere and global temperatures?

A24.2. For the last 160,000 years, let me ask your question in a different (and more revealing) way. If you told me the levels of greenhouse gases during the past 160,000 years, could I tell you what the polar temperatures would be? The answer, obvious from the observations, is no.

Q24.3. What do you believe are the reasons for these apparent contradictions to the greenhouse theory?

A24.3. I am unsure what you mean by the greenhouse theory. If the theory is that longlived greenhouse gases like carbon dioxide are the dominant determinants of climate, then the observations show this to be wrong. The reason why it is wrong is that the long-lived greenhouse gases are only one of many factors determining

« PreviousContinue »