The influential and widely discussed 2018 report of the United Nations Intergovernmental Panel on Climate Change (IPCC) concludes generally that the Earth is warming; that any increased warming will raise sea levels, harm coral reefs, and reduce crop production; that the warming is primarily man-made, the result of increasing amounts of trapped greenhouse gases, (especially carbon dioxide) in the upper atmosphere; and that it makes scientific and economic sense to reduce CO2 emissions now with petroleum-based energy taxes and regulations before more environmental damage is done.
There is a broad consensus among climatologists that global warming is fact and requires a strong political response in order to prevent weather and economic-related calamities from occurring within the next 10 or 20 years. However, there is also a strong minority position among some scientists and economists that is both skeptical of prevailing climate change science and also of the necessity for any governmental response to the alleged environmental dangers.
The scientific evidence on warming is reasonably clear: There has been a slightly more than 1 degree Celsius increase in atmospheric temperature since 1880 up to the present. Over those many decades, there have been periods of warming; periods of cooling; periods where no major changes have occurred; and, more recently, a relatively sustained period of warming. Most climate scientists expect the current warming trend to continue (absent any CO2 reductions) into the foreseeable future with substantial weather related problems (costs) if the warming advances another half degree Celsius or more.
There are several problems with this scenario. The first is that if the current warming trend moderates somewhat, stops all together, or reverts to a period of modest cooling, then few of the calamitous events predicted will occur within the IPCC benchmark 2030-2040 time-frame. The second is that it is still unclear whether warming actually generates more severe weather patterns as is frequently assumed. For example, the incidence of severe tornado activity (F3+) in the U.S. trends downward over the last 5 decades and 2018perhaps the warmest year on recordmarked a 13 year low.
Finally, any forecast of anything (GNP, divorce rates, cell phone sales) 10 to 20 years out has almost zero reliability and almost no chance of being correct. There are simply too many known variables that could change and skew the results; in addition, there are an unknown number of new variables that could arise that would work to radically alter outcomes predicted by climate models. Indeed, the spotty history of previous climate modeling should throw caution to the wind concerning all current predictions.
A far more serious problem, however, is that it is not entirely certain that man-made CO2 emissions are, if fact, driving temperature change in the first place. Carbon dioxide is a relatively minor greenhouse gas and the statistical association of specific levels of carbon emissions with specific temperature change is not impressive. And while CO2 emissions have steadily increased for many decades (much of it from expanding industrial activity in India and China) the Earths temperature, though trending upward, has displayed a marked variability over time. This suggests that there may be other factors aside from CO2 that are actually driving temperature.
One of the more likely candidates that would explain the variability of temperature over time, not unexpectedly, is the variability associated with solar activity. Indeed, the correlation of solar activity (surface temperature changes, sun spot cycles) with temperature variability may be far more robust than any CO2/temperature association. Are increasing CO2 levels irrelevant? Probably not entirely, but it is yet to be established beyond doubt that CO2 levels are the primary culprit in any warming scenario.
Yet if CO2 levels are not the primary driver of temperature change, then the entire economic and political case for carbon taxes and other regulations on emissions is severely weakened. Why should we increase the cost and price of energy generated from oil and natural gas if reducing emissions would produce no discernible environmental benefit? After all, there is one thing in this debate that is absolutely certain: Raising energy prices would harm consumers of energy. It would lower the standard of living of everyone and hurt low income households the worst. Thus, even though some advocates of energy regulation would frame their case in lofty moral terms, there is simply nothing inherently moral about inflicting costs on society without any predictable social payoff.
Some of us are old enough to remember the media scare concerning global cooling in the early 1970s. We were all going to freeze in the dark unless the government did something post haste. That concern looks relatively silly today. Perhaps the same thing will be true about the current climate change hysteria.