The central issue in the maddeningly, intransigent climate change debate is equilibrium climate sensitivity (ECS).
ECS measures the climate's response to increasing levels of atmospheric CO2. Specifically, it is the increase in the global average temperature anomaly (GATA) produced by a doubling of the quantity of CO2 injected into the atmosphere. For climate change policy, nothing else matters. The type and magnitude of phenomena attributable to current and future warming depends on the value of ECS, as does the type and magnitude of appropriate climate policy.
In its latest climate assessment report (AR5), the United Nation's (UN) Intergovernmental Panel on Climate Change (IPCC) states that the ECS "is in the range 1.5 °C and 4.5 °C (high confidence)." If the actual ECS was less than 1.5 °C, future warming would be tolerable to humans (though intolerable to the climate change theory of climate cultists). An ECS of 2 °C is a level of anthropogenic global warming (AGW) to which humanity could adapt; indeed, it may be beneficial to humans. An ECS in the neighborhood of 2.5 °C would require more mitigation (e.g., non-trivial reductions in greenhouse gas (GHG) emissions) than adaptation. By 3 °C, AGW transitions to catastrophic AGW (CAGW), with extreme climate damage likely. An ECS of 4.5 °C is apocalypse territory. Beyond that, contact Al Gore.
Now, despite its declaration of high confidence, the IPCC's ECS range is too wide, and useless to policymakers. At the low end, doing nothing seems like a reasonable policy. At the high end, we should move to mountains, preferably the mountains of Canada, and build dikes around our solar-powered, doomsday cities.
The IPCC's 2007 report (AR4) gave an ECS range and a "best estimate" (namely, 3.0). But no best estimate was given in AR5. The reason: a significant discrepancy between observation-based estimates and IPCC climate model estimates. Of 19 observational-based studies of ECS, 11 showed values below 1.5 °C -- i.e., below what the IPCC said was the minimum. Could this be the work of the "shoddy scientists" and "extreme ideologues" that John Kerry warned us about -- the ones (in this case, 11 studies) we should not allow "to compete with scientific fact"?
Apparently so. Such "scientific facts" can only weaken Kerry's hand in his climate change negotiations -- which require a large ECS to elevate global warming to the status of pandemics, poverty, terrorism, and weapons of mass destruction. According to the New York Times, he wants to be "the lead broker of a global climate treaty in 2015 that will commit the United States and other nations to historic reductions in fossil fuel pollution." Little, not even scientific uncertainty, will stand between Mr. Kerry and an historic treaty enshrining his name. Rest assured that in advancing US interests, Kerry will fully rely on the negotiating skills he has demonstrated in his work on the Syrian chemical weapons deal, the Iranian nuclear weapons agreement, the ISIS coalition structure, and the Israeli-Palestinian peace treaty.
In the meantime, under the auspices of its National Climate Assessment (NCA), the Obama administration is moving forward aggressively with its climate change policies, undeterred by the ambiguity of ECS science. To Mr. Obama, the apocalypse is already in progress. For example, his NCA asserts:
"Sea level rise, storm surge, and heavy downpours, in combination with the pattern of continued development in coastal areas, are increasing damage to U.S. infrastructure including roads, buildings, and industrial facilities, and are also increasing risks to ports and coastal military installations. Flooding along rivers, lakes, and in cities following heavy downpours, prolonged rains, and rapid melting of snowpack is exceeding the limits of flood protection infrastructure designed for historical conditions."
Climate havoc of such magnitude corresponds to an ECS exceeding 3.0, putting the planet on the fast track to CAGW, and NCA recommendations on the fast track to trillions of dollars.
If it were true. Recent studies indicate an ECS significantly lower than both IPCC and the NCA estimates. According to the Cato Institute, since 2011, 14 peer-reviewed studies have found the earth to be much less sensitive to CO2 increases than previously thought. "Most of these sensitivities are a good 40% below the average climate sensitivity of the [IPCC] models." The most recent study puts the ECS at 1.64 °C, "a value that is nearly half of the number underpinning all of President Obama’s executive actions under his Climate Action Plan." Such low estimates are hardly the stuff of rapid ice melt, surging sea levels, and extreme weather events. We may be transitioning to DAGW (decrepit AGW; for climateers, disconcerting AGW).
The current, and continuing, warming pause further erodes the NCA position. In defiance of the more than 100 billion tons of CO2 that have been spewed into the atmosphere since 1998, the temperature has not increased. The AGW hypothesis called for it to rise; the CAGW hypothesis called for it to shoot through the roof -- as Al Gore demonstrated in An Inconvenient Truth, by propelling himself on a pneumatic scissors lift to ever-loftier heights of temperature. But the GATA hasn't budged.
Climate scientists are aghast. They can't explain the missing heat. At least a dozen possibilities are discussed in A Sensitive Matter and Climate change: The case of the missing heat. Some don't even involve CO2. It might be aerosol particles, reflecting heat back into space. It could be clouds. And let's not forget the sun, that has been experiencing a weak "solar maximum." Perhaps the heat is hiding in the ocean, over 700 meters below the surface, or deeper still. It might be moving around -- shuttled by the Pacific Decadal Oscillation (PDO), alternately favoring El Niño and La Niña in 15-30 year cycles.
But, "it might be that the 1990s, when temperatures were rising fast, was the anomalous period." Or, "as an increasing body of research is suggesting, it may be that the climate is responding to higher concentrations of carbon dioxide in ways that had not been properly understood before." The science grows unclearer.
Possibly more disconcerting than the ambiguous ECS or the perplexing warming pause are the unfounded claims of damage from future warming. General Circulation Models (aka, Global Climate Models) (GCMs), used to project future warming, have consistently overstated temperature trends. They are plagued with flaws that could invalidate their reliability. The IPCC itself concedes as much. As Steven Hayward observed in Climate Cultists,
While climate skeptics are denounced for mentioning “uncertainty,” the terms “uncertain” and “uncertainty” appear 173 times, while “error” and “errors” appear 192 times, in the 218-page chapter on climate models in the latest IPCC report released last September . As the IPCC admits, “there remain significant errors in the model simulation of clouds. It is very likely that these errors contribute significantly to the uncertainties in estimates of cloud feedbacks and consequently in the climate change projections.”
Why, then, is the Obama administration clamoring for urgent, profligate government action? According to AR5, there is low confidence that today's "sea level rise, storm surge, and heavy downpours" can be attributed to AGW. Nor can droughts, wildfires, and other "extreme weather" events -- no matter how many times catastrophists say otherwise. Such events require climate-ravaging temperatures that, having been projected by flawed GCMs, may never be reached. Maybe it's too soon for the wholesale replacement of extraordinarily cheap and reliable fossil fuels with extraordinarily expensive and unreliable wind and solar farms. After all, history is replete with similarly grand schemes that shattered the dreams of the central planners who concocted them (the Soviet Union's collectivization of farming and China's 'Great Leap Forward' come to mind).
But, what if Obama and Kerry are right? After all, AGW is a plausible theory, there has been post-industrial warming (a 0.8 °C increase since 1850), and, through the burning of fossil fuels, humans (especially in China and India, where carbon emissions are sharply rising, while US emissions are declining) pump immense quantities of CO2 into the atmosphere. Who knows, the warming could resume -- possibly at the alarming rates assumed in the NCA?
It is precisely this possibility that Messrs Obama and Kerry flaunt, in making the case for immediate "climate action." The "cost of inaction" is too great, they tell us; we can't afford to wait. The possibility of abrupt and rapid temperature rise, however remote, is of such grave concern that, last June, president Obama used his executive authority (bypassing Congressional approval) to issue new EPA rules requiring US power plants to cut CO2 emissions 30% by 2030. Yet, with full compliance through 2100, these rules will reduce the GATA by an unnoticeable 0.02 °C. But Americans whose electricity is generated by coal-fired power plants will painfully notice that it's the "cost of action" that's too great.
Moreover, according to the EPA’s own model (the Model for the Assessment of Greenhouse-Gas Induced Climate Change (MAGICC)), a 100% reduction in US emissions would reduce the end-of-century GATA by a distressingly futile 0.14 ºC. Who could possibly be undisturbed by this result -- other than the EPA employee who is, no doubt, in line to receive a Champions of the Earth Award for inspiration, in coining the model's name.
More unsettling are the results of integrated economic and climate models (described in Examining the Threats Posed by Climate Change) that measure the cost of policy action to mitigate climate damage. For scenarios similar to those assumed by the NCA ( e.g., an ECS of 3.2 ºC, resulting in a 3.4 °C temperature increase by 2100), the cost to the US economy of global climate inaction (i.e., unmitigated warming through 2100) is a 1.8% reduction in GDP. The cost of global climate action (that prevents a 2.0 ºC GATA increase) reduces US GDP by 3.2%. Thus, with the Obama administration's "climate insurance" investment, the abatement cost could be twice the cost of the averted climate damage -- not unlike its Solyndra investment, where solar panels costing $6.29/Watt to manufacture were being sold for $3.42/Watt.
Very likely, we can afford to wait. NCA plans (carbon regulation, carbon taxes, cap-and-trade, global emissions treaties, etc.) to control climate are, at best, an expensive fantasy -- a green dereism that is anathema to the almost six of the seven billion people inhabiting the planet, who have no choice but to burn increasingly large quantities of affordable fossil fuels. Who, but deluded ideologues, would insist on draconian climate policies that will be ignored by the vast majority of the world's population; that will have no measurable effect on GATA, if they are not enforced globally; and that would cost the US economy twice as much as the damage they save, if they could be enforced? All this to insure against the possibility that the warming resumes and follows a hellish pace for the next 86 years.
With AR5, the IPCC's fifth attempt to quantify ECS, this most important parameter of climate science remains too vague for identifying the appropriate climate change policy. We simply do not know, with any precision, the Earth's climate sensitivity. It's obscurity is exceeded only by the idiosyncrasies of atmospheric CO2, the biases of GCM errors, and the cajolement by which countries such as China and India will be brought into emissions compliance. The essence of AR5 is uncertainty, garnished with ambiguity and doubt.
To skeptics (aka, deniers, flat-earthers, merchants of doubt), the recent estimates of dramatically lower ECS dictate caution, and possibly a re-examination of the AGW hypothesis. Common sense dictates the need for much greater scientific clarity. Use the warming downtime to find the missing heat and the modeling errors -- and a better case for urgent, radical action. The integrated modeling results, which show the alarmingly high cost and low effectiveness of such action, make a more compelling case for inaction. Perhaps a re-evaluation of current policy is in order.
Not likely. As Hayward noted,
"Despite all this, there has been not even the hint of a second thought from the climateers, nor any reflection that their opinions or strategies could bear some modification. The environmental community is so deeply invested in looming catastrophe that it’s difficult to envision a scientific result that would alter their cult-like bearing."
Accordingly, on the day that AR5 was released, John Kerry rushed out to declare,
"Once again, the science grows clearer, the case grows more compelling, and the costs of inaction grow beyond anything that anyone with conscience or common sense should be willing to even contemplate."
Once again, John Kerry's arrogance grows clearer, and most unsettlingly so to those who believe that precision in climate science should trump hysteria in climate policy -- those who, in the contemplation of the Obama administration, are the "extreme ideologues."