I want to change public concern from Global (GW) to Global Cooling (GC). Presented here are three arguments in favor of such a drastic shiftwhich involves also a drastic shift in current policies, such as mitigation of the greenhouse (GH) gas carbon dioxide.
My main argument relies on the fact, backed by historical evidence, that cooling, even on a regional or local scale, is much more damaging than warming. The key threat is to agriculture, leading to failure of harvests, followed by famine, starvation, disease, and mass deaths.
Also, GC is reasonably sure, while GW is iffy. The evidence, again, is historicalfrom deep-sea sediment cores and ice cores. Our planet has experienced some 17 (Milankovitch-style) glaciations in the past 2 million years, each typically lasting 100,000 years, interrupted by warm inter-glacials, typically of around 10,000-yr duration. The most recent glaciation ended rather suddenly about 12,000 years ago. We are now in the warm Holocene, which is expected to end soon.
In fact, we may have already entered into the next glaciationas we can discover only in retrospect. (Past cycles suggest a very gradual cooling initiallywith ice accumulation and a drop in global sea levels, a decrease in atmospheric CO2 into the cooling oceans and lowest temperatures occurring only much later in the cycle.)
Archeological data show that the recent glaciation wiped out the Neanderthalers and much of the fauna that constituted their source of food. Most of humanity may not survive the next, inevitable glaciation.
We need to consider also the warming-cooling (Dansgaard-Oeschger-BondDOB) cycles, which seem to be solar-controlled and have a period of approx 1000-1500 years; its most recent cooling phase, the Little Ice Age (LIA), ended about 200 years ago. For details, see Unstoppable Global Warming: Every 1500 Years by Singer and Avery .
The LIAs are not nearly as severe as the major glaciations; yet they present an important threat to the food supply and to current civilization. Available technology seems adequate to assure human survivalat least in industrialized nations. The main threat is warfare, driven by competition for food and other essential resources. With nuclear weapons and delivery systems widely dispersed, the outcome of future wars is difficult to predict.
Geo-Engineering: Overcoming a Future Ice Age
In a word: the possibility of using technology to overcome a future cooling looks promising for both types of ice ageswith relatively low cost and low risk to the physical and biological environment.
Geo-Engineering has generally been discussed in relation to GWmost recently in two reports issued by the US National Academy of Sciences-National Research Council. The schemes most favored include either reduction of solar intensity (by increasing Earths albedo (the fraction of solar energy reflected back into space) or reduction of the atmospheric level of carbon dioxide (under the unproven assumption that the increasing level of the GH gas CO2 is responsible for such a GW). Unfortunately, both approaches are costly and have undesirable side effects.
With regard to the Milankovitch cycles, there is of course little chance of changing the astronomical parameters that influence the cycles. One can dream up engineering schemes to increase solar flux to the Earths surfaceeither by increasing solar intensity or by reducing general albedo. Both approaches are costly and risky.
The most promising method is to find a triggera phenomenon that initiates the glaciation. The most common suggestion is a high-latitude snowfield that somehow survives summer melting. It can then grow from year to year in extent and thickness and develop into an ice sheet by a kind of positive feedbackthanks to the high albedo of snow and ice.
The easiest way to locate such triggers is by digital comparison of successive images from existing weather satellites. This non-intrusive scheme costs very little and presents no risks of any kind; it is simply a software program that processes available data in a special way. It is fairly easy to establish an automatic routine to accomplish this task.
Once such growing snowfields have been located, they can be covered with black soot to decrease albedo. The summer sun can then do its work. How much soot? A certain amount of experimentation is required to answer the question. The best way to produce and spread soot particles can again by found by experiment; it looks like a rather simple technical issue, akin to crop-dusting in agriculture.
The problem appears to be rather different for DOB cycles; there may not be any triggers to initiate the cold phase of a cyclealthough clues on timing may be derived from solar observations. These clues may simply be the time-history of sunspot numbers; but more sophisticated techniques to monitor the Sun are just now becoming available.
The aim would be to eliminate the cold phaseor at least diminish it. The problem is rather complicated; judging from available but imperfect and incomplete data. Observations between 1400 and 1800 AD of the Little Ice Age show that cooling appears to be regional rather than global; in addition, the cold phase is not continuous but consists of decades-long frigid intervals, with warmer periods in between.
Obviously, there is much scope here for research on how to ameliorate DOB cooling. One suggestion is to make use of GH effects. But CO2 is not the answer; its atmospheric lifetime is too long and its distribution is globala poor match to what is required. In addition, CO2 effectiveness is questionableor at least controversialjudging by the current temperature plateau (a.k.a. pause or hiatus) that has lasted nearly 20 yearsand perhaps even much longer.
My personal suggestion has been to create regions of cirrus near the tropopause by injecting water in the form of mist or droplets, leading to ice particlesakin to contrails from aircraft. The scheme would create regions of strong GH forcing and seem to fit the twin requirements of regionality and moderate lifetime. How much water is needed? How often to injectand other important but more detailed parameters? Again, we need to learn by experimentation.
In my opinion, there is little doubt that a near-term cooling is among the major calamities facing the population on our planet; concern about global warming is entirely misplaced. A Little Ice Age (DOB cooling) may arrive within decadesperhaps much sooner. The end of our warm Holocene inter-glacial is rapidly approaching. There is no time to lose in preparing for survival. A paradigm change is essential.
Instead of fiddling with apportionment of CO2 quotas among different nations, we should face realities: CO2 forcing of climate seems largely offset by internal atmospheric negative feedback. In any case, CO2 forcing is largely saturated spectroscopically; there is little chance of exceeding or even reaching the artificial temperature goal of 2 degrees that politicians have adopted.
No effective quota system will emerge at the forthcoming climate conference in Paris in December 2015, as long as developing nations, like India, aim to overcome poverty by assuring their citizens of reliable, secure, and cheap energy from fossil fuels. The United States needs to learn this lesson also.