On the Helix Facebook page yesterday, Richard Betts writes about High-End Climate Impacts and Extremes.
He claims “the chances are that global warming will exceed the 2°C “guardrail” that the EU and UN aim to stay below,” and doesn’t disagree with alarmist interpretations of the scale and effects of man-made global warming, such as the possibility of 6°C warming. But “science” says little about our future climate. Why?
Because the future climate depends, not on nature, surprisingly, but on future human emissions of CO2. The IPCC makes up “scenarios” and imagines what might occur under each of them. The imagined scenarios, called Representative Concentration Pathways (RCPs), are ranked according to their future levels of atmospheric CO2, with the most extreme of them called RCP8.5, which stands for a global level of radiative forcing of 8.5 W/m2 by 2100.
It is highly contentious when, or even whether, we will achieve such a high level. Despite Betts’s naively confident reference to “the various computer climate model simulations of how the climate responds to these GHG changes” (as though it’s all based on known rules of physics and chemistry), the relationship between atmospheric carbon dioxide and warming is programmed into the models. The warming is most emphatically not based entirely on known physical laws and it’s not an output from the models. If it was, we wouldn’t see such huge error margins in the graphs of future temperature, sea level, rainfall, drought, storminess, humidity and so on. If we thought the models were accurate, we’d only need one of them, don’t you think? Instead, we have between 7.5 and 9, or about 24, or 50, or 60, or over 90—depending on who’s counting.
But the most significant aspect of the scenarios is their huge range of possibilities, and nobody knows which one represents our future. RCP8.5 assumes we will make no change at all to our emissions but carry on burning hydrocarbons freely. This will mean our emissions will rise as efficient production methods powered by energy from hydrocarbons spread to developing countries and as the population increases.
You might think that dooms us to the worst possible fate and will destroy the environment, but there’s no sign of it so far. There is every reason to expect life to continue as usual. Why?
Because for the last 20 years, our emissions have gone on increasing merrily to record levels. But all that time the global average surface temperature has been so flat it’s impossible to say whether the globe has been warming or cooling. There is no cause for concern. The temperature is not rising dangerously and the world is not about to end.
In addition, there is as yet no evidence of a mechanism by which our minute contribution to the atmospheric concentration of CO2 manages BY RADIATION to warm the oceans (imagine holding a lit cigarette above the cold water in a bath; the water is unlikely to warm). This is not widely acknowledged. If there really is no such mechanism, it is axiomatic that strident demands to eliminate our emissions to stop the seas rising dangerously are unnecessary.