Alarm has spread to staid organisations like the International Energy Agency. In 2011 it declared: ‘On planned policies, rising fossil energy use will lead to irreversible and potentially catastrophic climate change.’ Late last year a report by the World Bank warned that ‘we’re on track for a 4°C warmer world marked by extreme heat-waves, declining global food stocks, loss of ecosystems and biodiversity, and life-threatening sea level rise.’
A world warmed by four degrees
It’s hard to communicate to the public what a world warmed by 4ºC will be like, or even that the IEA and the World Bank should be taken seriously. After all, for many people one unseasonable snowstorm is enough to nullify decades of painstaking scientific study. And psychologists have discovered that, after accounting for all other factors, when people are put in a room and asked about climate change they are significantly more likely to agree that global warming is ‘a proven fact’ if the thermostat is turned up.
So for at least a decade climate scientists have been disturbed by the widening gap between the actions demanded by the evidence and those being implemented or even considered by the major polluting nations. At the same time, their work began to focus on the dangers of feedback effects in the climate system, that is, processes that amplify or dampen the direct warming effect of rising greenhouse gases.
For example, as warming melts the Arctic ice cap, the exposed water is darker than the highly reflective ice it replaces and so absorbs more heat from the sun. Many in the expert community received a fright from the dramatic declines in Arctic summer sea ice in 2005 and especially 2007. And the melting of sea ice this past northern summer set new records.
The study of feedbacks has been closely related to another idea emerging in the scientific literature – that of tipping points.
Small changes in one element of the climate system may initially have only small effects, but at some point a threshold may be crossed where the system, driven by amplifying feedbacks, flips into a new state. Palaeoclimatologists have discovered many instances in the Earth’s geological record of the climate shifting abruptly from one state to another, within a few decades. The esteemed palaeoclimatologist Wally Broecker warned: ‘The palaeoclimate record shouts out to us that, far from being self-stabilizing, the Earth’s climate system is an ornery beast which overreacts even to small nudges.’
Against this background, climate scientists began to talk about possible responses to a climate emergency – such as a massive methane release with rapid melting of permafrost, the collapse of the West Antarctic ice sheet, or rapid dieback of the Amazon forests.
Any of these could quickly shift the global climate into a new state, and there would be no way of recovering the situation. How, they asked, could we intervene to prevent these things happening? If Plan A, persuading the world to cut emissions, is failing, shouldn’t we have a Plan B? And so in the last few years, research into various schemes to engineer the climate has been accelerating rapidly.