Cop26 Global Temperature Rise: COP26: What if the increase in global temperature reaches 3 degree Celsius? – cop26 what if the global temperature rise reaches 3 degree celsius
In the Paris Climate Agreement, countries around the world have pledged not to allow global warming before the Industrial Revolution to exceed 1.5°C. Even if all countries meet their current commitments to reduce carbon emissions, we will still see an increase in global temperature by about 2.7 °C. No wonder nearly two-thirds of the authors of the Intergovernmental Committee on Climate Change, taking part in a new survey in the journal Nature, estimate the rise to be three degrees Celsius or more.
So how different would the effects of climate change be on a three degree Celsius rise compared to 1.5 degree Celsius? It is important to understand at the outset that even if the effect increases with temperature – the effect on a temperature rise of three °C will be more than twice as high as that of 1.5 °C. This is because the increase in global temperature is already about 1 °C above pre-industrial levels, so the effect at three °C will be four times greater than at 1.5 °C (2 °C from now compared to 0.5 °C). Growth).
Growth accelerates as temperature rises
In practice, the effects do not necessarily increase linearly with temperature. In some cases the growth accelerates as the temperature rises, so the effect at three °C can be more than four times the effect at 1.5 °C. At the most extreme, the climate system may pass some ‘tipping point’ (the point at which a series of smaller changes or events become significant enough to cause a larger, more significant change) leading to a significant change in policy or stance. It is possible. Two years ago colleagues and I published research looking at the effects of climate change on different levels of global temperature rise.
We found, for example, that the global average annual probability of a large extreme heatwave increases from about 5 percent in the 1981–2010 period to about 30 percent at 1.5 °C but 80 percent at 3 °C. . The average probability of river flooding expected in years increases from two percent to 2.4 percent at 1.5 °C at present, and doubles to 4 percent at 3 °C. At 1.5 °C, this ratio of time to drought nearly doubles, and at 3 °C it more than tripled. There are certainly some uncertainties in these figures where the scale of the possible outcomes may increase with the increase in temperature.
Flood risk will increase especially rapidly in South Asia
There is also worldwide variability, and this variability increases with temperature rise, in effect increasing geographic disparities. The risk of river floods will increase especially rapidly in South Asia, and droughts will be greater in Africa than in the world. The difference between 1.5 °C and 3 °C could be even greater in places like the UK where the effects of climate change would be relatively less severe than elsewhere. The actual consequences for people will depend on how these direct physical effects – droughts, warming waves, rising sea levels – affect livelihoods, health and the interrelationship between the elements of the economy.
Our experience during COVID-19 suggests that what appears to be a relatively minor initial disturbance to the system can lead to large and unpredictable effects, and we can expect the same with climate change. If temperatures rise and physical effects such as melting of glaciers or extreme weather conditions are often non-linear, much of the effects of temperature rise and on people, societies and economies are likely to be non-linear. This means that the world at a three degree Celsius rise would be much worse than a 1.5 degree Celsius world.
(Nigel Arnell, University of Reading)
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