The Difference Half A Degree Of Global Warming Can Make

The recent ‘Global Warming of 1.5 C’ report of the Intergovernmental Panel on Climate Change highlights several climate change impacts that could be avoided by limiting global warming to 1,5 C, compared with 2 C or more. For example, at 1,5 C warming, the Arctic Ocean is likely to be free of sea ice in summer just once a century on average, whereas at 2°C global warming, the likelihood rises to once a decade.

- Denene Erasmus

Human activities are estimated to have caused 1°C of global warming above pre-industrial levels, with a likely range of 0,8°C to 1,2°C. Current models show that global warming is likely to reach 1,5°C between 2030 and 2052 if it continues to increase at the current rate.

In addition, warming from emissions originating in human activity from the pre-industrial period to the present will persist for millennia and continue to cause long-term changes in the climate system, such as sea-level rise. Impacts on natural and human systems from global warming have already been observed.

Many land and ocean ecosystems have changed due to global warming. Future climate-related risks depend on the rate, peak and duration of warming. In the aggregate, they will be larger if global warming exceeds 1,5°C before returning to that level by 2100 than if global warming gradually stabilises at 1,5°C, especially if the peak temperature is high, for example about 2°C. Some impacts, such as the loss of an ecosystem, may be long-lasting or irreversible.

POTENTIAL IMPACTS AND RISKS

Some climate characteristics will be influenced by the conditions in particular regions and by the extent to which temperatures rise due to global warming. They include: mean temperature in most land and ocean regions; hot extremes in most inhabited regions; heavy precipitation in several regions; and the probability of drought and precipitation deficits in some regions.

It is projected that, by 2100, global mean sea-level rise will be about 0,1m lower with global warming of 1,5°C than with a figure of 2°C. The sea level will, however, continue to rise well beyond 2100, and the magnitude and rate of this rise will depend on future emission pathways.