Willie Soon

Introduction 1. The relationship between atmospheric CO2 and CH4 concentrations, temperature, and ice-sheet volume 2. Atmospheric CO2 radiative forcing as an amplifier of glacial-interglacial climate change 3. Glacial-interglacial climate change: the role of orbitally moderated insolation forcing at local and regional scales compared with the effects of global radiative forcing from changing CO2 concentration 4. Problems with CO2 amplification of global mean temperature: computer simulations and quantitative data

The relationship between atmospheric CO2 and CH4 concentrations, temperature, and ice-sheet volume

CO2 content being driven by change in temperature using the Vostok data Southern Hemisphere forcing scenario: External orbital insolation triggered the fast and large changes in the air temperature in the SH → cause responses in deep ocean properties & global carbon cycle → changing levels of atm. CO2 Northern Hemisphere forcing scenario: northern- lead, also proposes atm.CO2 as the essential amplifier of the warming and cooling and hence the waxing and waning if global ice volume

Atmospheric CO2 radiative forcing as an amplifier of glacial-interglacial climate change It’s still unclear as to whether such a plausible CO2- amplification scenario can be quantitatively confirm with evidence available to date.

Glacial-interglacial climate change: the role of orbitally moderated insolation forcing at local and regional scales compared with the effects of global radiative forcing from changing CO2 concentration

At this stage, it’s relevant to emphasize that the popular scenario for potential episode release of methane hydrates may not be so straightforward. 1. Milkov has lowered the previously accepted high estimate of global hydrate-bound gas from 21x10 15 m 3 → 1 to 5x10 15 m 3 2. Possibly incorrect interpretation of the large delta13C excursions in the records of planktonic and benthic foraminifera as clathrate-derived methane release.

3. Bhaumik and Gupta have recently identified five major episodes of methane release since 3.6 million years BP, these they link to reduced hydrostatic pressure connected to lowered sea levels and intense glacial events, roughly coinciding with increased glaciation in the NH. Thus, many numerical attempts to quantify the impacts from variations in two minor greenhouse gases, CO2 and CH4, don’t confirm their predominant roles in explaining the large amplitude changes in thermal, hydrologic, and cryospheric history during glacial- interglacial transitions.

Persistent solar insolation forcing at key seasons and geographical locations, and closely related thermal, hydrological, and cryospheric changes may be sufficient to explain regional and global climatic changes during glacial-interglacial transitions.

Problems with CO2 amplification of global mean temperature: computer simulations and quantitative data GCM Imposing a CO2 radiative forcing estimate of about 2.5 W/m 2 for the 80ppm change, which will trigger a warming 2-3C fall far short of the calibrated 10-12C in Antarctic temperature change.

Low tilt angle, high eccentricity More extensive snow accumulation

The examples serve only as the sufficient but not necessary of orbital insolation forcing in accounting almost fully for conditions and changes during the glacial-interglacial transitions, without the need to invoke the argument for CO2 as the predominant amplifier of those changes.

Conclusion No quantitative evidence that varying levels of minor greenhouse gases like CO2 and CH4 have accounted for even as much as half of the reconstructed glacial- interglacial temperature changes. This paper shows that changes in solar insolation at climatically sensitive latitudes and zones exceed the global radiative forcing of CO2 and CH4.

There are still questions about how orbital forcing explain glaciation and deglaciation over the past few million years with the 100-kyr glacial-interglacial cycles not fully explained. However, the popular notion CO2 and CH4 radiative forcing as the predominant amplifier of glacial- interglacial phase transitions can’t be confirmed.

Our basic hypothesis is that long-term climate change is driven by insolation changes, from both orbital variations and intrinsic solar magnetic and luminosity variations.