and agriculture--global average temperature was 1-2° C above current values. Work by Domack et al. shows that Antarctic glaciers were expanded during this period, locking up moisture and countering sea level rises. Those who fear large sea level rise from a 1-2° warming during the next century should be comforted, but, in reality, are discomforted!

During the depths of the recent "Little Ice Age", Northern Hemisphere temperatures were 1-2° C cooler than today. Bond et al. recently demonstrated in Science, using ocean sediment records, that there is a natural swing in the earth's mean temperature with a periodicity of 1400 years that explains in large part these variations. And the point in the cycle where we currently reside is one in which there would have been a large warming of the 20th Century, whether or not man had influenced the greenhouse effect.

Temperature Record

Q11. There seems to be some disagreement regarding interpretation of the historical temperature record between you and Dr. Watson, who testified that, "If you actually go back before... to 1860, the 1900s, 1910s were particularly cold so this somewhat distorts the increase between 1900 and 1940..." Yet, later in the discussion you suggested that the record from 1860 to the early 1900s was “constant,” and Dr. Watson agreed. However, you appeared to disagree with Dr. Watson's characterization of the record (quoted above), terming it "misrepresented and exaggerated.” It would appear, based on the data in Figure 3.3 (page 143) of the 1995 IPCC report, The Science of Climate Change, that the temperature from 1860 to about 1915, when temperature began to increase consistently, was indeed relatively constant, fluctuating between -0.2°C and -0.5°C relative to the 1961-1990 average. Could you please elucidate on the point your disagreement with Dr. Watson?

All. Dr. Watson attempted to accuse me of selecting a starting point in the IPCC surface temperature record that distorted the magnitude of the increase between 1900 and 1940. The rapid warming of the early 20th century (which is actually most concentrated between 1910 and 1940) presents great problems to the climate models because it clearly takes place before there was much of a change in the greenhouse effect! It is more likely to be of the nature described in my answer to the previous question, which would only leave a small remainder (0.3° C) of 20th century warming that could be attributable to greenhouse changes. This is a factor of six underneath the warming forecast by the climate models that served as the basis for the Framework Convention on Climate

I was really shocked at Watson's contention. As the head of the IPCC, he had brought the most recent summary report to the hearing. I then opened it to page 424, which details observed and modelled global average temperatures. The illustration is shown as Figure 4 here.

I then asked Watson if in fact there was a decline in temperature from 1860 to the early 1900s, and he agreed in fact that there was none.

My point was that Watson was attempting to accuse me of distortion, either by asserting something he (as head of IPCC) must have known to be untrue, or simply that he was not that conversant with the historical record.

Figure 4.Observed and modelled global temperatures, given in the 1995 IPCC report. The modelled temperatures are those calculated for greenhouse effect changes only. Greenhouse-only models served as the basis for the Framework Convention on Climate Change.

REFERENCES

Bond, G., et al., 1997. A pervasive millennial-scale cycle in the North Atlantic Holocene and glacial climates, Science, 278, 1257–1266.

Domack, E.W., A.J. Jull, and S. Nakao, 1991. Advance of East Antarctic outlet glaciers during the Hypsithermal: Implications for the volume state on the Antarctic ice sheet under global warming. Geology, 19, 1059–1962.

Kerr, R.A., 1997. Model Gets It Right-Without Fudge Factors. Science, 276, 1041.

Michaels, P.J., S.F. Singer, and P.C. Knappenberger, 1994. Analyzing Ultraviolet-B Radiation: Is There a Trend? Science, 264, 1341-1342.

Omuhra, A., M. Wild, and L. Bengtsson, 1996. A Possible Change in Mass Balance of Greenland and Antarctic Ice Sheets in the Coming Century, Journal of Climate, 9, 2124-2135.

46-495-19

CONTENTS

PREFACE

FOREWORD

IPCC SECOND ASSESSMENT SYNTHESIS OF SCIENTIFIC-TECHNICAL INFORMATION RELEVANT TO
INTERPRETING ARTICLE 2 OF THE UN FRAMEWORK CONVENTION ON CLIMATE CHANGE..

1. Addressing the UNFCCC Article 2

2. Anthropogenic interference with the climate system

3. Sensitivity and adaptation of systems to climate change

4. Analytical approach to stabilization of atmospheric concentrations of greenhouse gases

5. Technology and policy options for mitigation

SUMMARY FOR POLICYMAKERS: THE SCIENCE OF CLIMATE CHANGE IPCC WORKING GROUP I

1. Greenhouse gas concentrations have continued to increase

2. Anthropogenic aerosols tend to produce negative radiative forcings

4. The balance of evidence suggests a discernible human influence on global climate

5. Climate is expected to continue to change in the future

SUMMARY FOR POLICYMAKERS: SCIENTIFIC-TECHNICAL ANALYSES OF IMPACTS, ADAPTATIONS

SUMMARY FOR POLICYMAKERS: THE ECONOMIC AND SOCIAL DIMENSIONS OF CLIMATE CHANGE -
IPCC WORKING GROUP III

43

7.

The social costs of anthropogenic climate change: Damages of increased greenhouse gas emissions

50