Global Warming / Climate Change and Variations in Solar Activity: Past, Present and Future?

Since the author’s first article on this subject, titled “Global Warming and the Sun”, was published in the CSEG Recorder in January 2000, the evidence that solar variations and other natural forces may in fact be the primary drivers of recent global warming have continued to grow. A briefer version of the above article was published in July 2000 in APEGGA’s monthly newspaper, the PEGG, and generated much controversy and discussion among the APEGGA membership. In March 2001, the PEGG published the author’s response to several letters to the editor that appeared in the PEGG’s “Reader’s Forum” regarding the July 2000 article. This response was titled “Sensible Global Warming Policy Is What We Need”.

Earlier climate modeling used the “Solar Constant” as the energy input into the Earth climate system, i.e. no change in energy input from year to year, an assumption that we now know is incorrect. Satellite observations of the energy that the Earth receives from the Sun, measured above the filtering effects of the Earth’s atmosphere, clearly show that it is not constant from year to year and that it varies roughly in-phase with sunspot activity, indicating changes in energy output at source. Another problem with the climate model predictions is that, due to the way the greenhouse effect works, they indicate that the lower troposphere (the lower few km of the Earth’s atmosphere) should warm at least as much as the surface air temperatures during a greenhouse warming. However, both balloon- and satellite-based observations of lower tropospheric temperature over the past two decades actually show a slight cooling trend at the same time that the surface air temperatures have been rising rapidly. The climate modelers have not been able to explain this discrepancy between their model predictions and the actual observations. Obviously the climate models do not as yet provide a sufficiently representative model of the Earth’s climate system.

Some climate modeling has been done using estimated variations in Total Solar Irradiance, a broadband measurement of incoming solar energy, which indicate that solar variations are a significant contributor to global warming and climate change. However, various parts of the solar spectrum vary quite differently than others as a function of time. Also, different parts of the incoming solar spectrum are reflected, absorbed or transmitted by varying amounts as a function of altitude and geographic position within the Earth’s atmosphere. Not until the climate models incorporate representative changes in both incoming solar spectral variations and the variations in the reflection, absorption and transmission coefficients of the Earth’s atmosphere as a function of latitude, longitude, altitude and time will they likely provide a reasonably accurate estimate of solar heating within the atmosphere and of the net solar energy that reaches the surface of the Earth to contribute directly to surface heating as a function of time.

However, one published climate model study may have approximately incorporated the effects of many of these various spectral changes as a function of time by optimizing their climate model outputs to provide the best possible match between predicted and observed surface air temperature variations. Figure 1 shows the best climate model result from Soon et al (1996) that included input from both solar and greenhouse gas variations. As you can see in this figure, the match between the predicted and observed temperature variations is incredibly good and indicate that over 80% of the warming of the 20th century, and also that of just the past couple of decades, may be attributable to solar variations alone. It has also been proposed that variations in solar activity control the El Niño and La Niña cycles, etc.

In August 2001, “The 1st International Conference on Global Warming and the Next Ice Age” was held in Halifax, Nova Scotia at Dalhousie University. This conference was co-sponsored by the Atmospheric Science Program at Dalhousie University, the Canadian Meteorological and Oceanographic Society, the American Meteorological Society and the European Space Agency. In a post-conference summary posted on the conference website, the organizers state, “More than a hundred scientists from thirteen countries attended the Conference. It was one of the largest meetings devoted exclusively to climate change ever held in Canada.” Further, “Fifteen of the scientists attending the Conference also served as coauthors or reviewers of the 2001 IPCC (Intergovernmental Panel on Climate Change) report, which represents the current “consensus” view on climate change, ascribing most of the current warming to the anthropogenic production of carbon dioxide. However, other views suggesting that a considerable fraction of the current warming trend may be caused by changes in ocean circulation, variability of solar output and by natural variability of a complicated nonlinear climate system were also presented.” Later, referring to the need for us to preserve a clean environment and save natural resources for future generations, the summary states, “This we will do because we want to do it, because it is the right thing to do, because we are considerate members of humanity, and not because of an exaggerated prediction of a climate catastrophe.” See the conference website listed in the references.

Variations in solar energy output will undoubtedly help to explain the comings and goings of the ice ages of the recent geologic past and climate change throughout the history of the Earth. Two “cosmogonic” isotopes, Beryllium-10 and Carbon-14, are both formed high in the atmosphere and their production rates are affected by variations in solar activity, and can be measured in glacial ice cores and in lake and ocean sediment cores, and offer significant potential to estimate solar variability over recent geologic time, i.e. over the last few tens of thousands of years to perhaps millions of years before present.

If solar variations are the primary driver of recent global warming, which does appear to be the case, then global temperature variations for the rest of the 21st century will depend mostly on what the Sun does next, not on our greenhouse gas emissions. Various predictions of the future course of solar activity indicate that solar heating, on time scales of a decade to a century, has either peaked or will peak shortly and then it will enter a roughly 100 year cooling trend. Therefore, the rapid rise in global surface air temperatures over the last couple of decades may soon come to a natural end if surface solar heating declines as expected.

Most paleoclimate data indicate that the warmest period in the present interglacial was about 5,000 to 8,000 years ago, and that we are already slowly headed into the next ice age. The next ice age is predicted to be at its coldest about 23,000 years from now, Imbrie and Imbrie (1979), although there is a large uncertainty in this prediction. The warming of the 20th century mostly appears to have simply been a natural, “short-term” warming blip along the way.

Obviously there are significantly negative effects of human activity on the environment and we do need to clean up our act to ensure the healthiest environment possible for all of us, and future generations, on this planet. However, it now appears that the contribution of increased concentrations of carbon dioxide and other greenhouse gases in the atmosphere to the observed surface warming has been greatly over-estimated. If our carbon dioxide emissions are not a significant problem, at least as far as global warming is concerned, then a reassessment of our global energy and environmental protection strategies are in order. Obviously we do need to clean up our exhaust emissions in general, particularly in urban areas, so a move away from gasoline-powered vehicles is desirable. However, since natural gas is the “cleanest” burning of the fossil fuels and if its carbon emissions are not a significant problem, then natural gas could be used to supply much of our overall energy needs for decades to come, rather than switching to more expensive nuclear or alternative energy options in the near future. Even oil and coal may not be as bad for the environment as previously thought, particularly if further reductions in the harmful emissions associated with the burning of these “dirtier” fossil fuels can be achieved.

Hopefully we will have the wisdom to focus our finite resources on the environmental problems that we are indeed responsible for and thus can be the most effective at mitigating; global warming does not appear to be one of them. This wisdom would leave more resources available for the many other problems that plague the human race.