New Delhi: Representatives of more than 150 nations are expected to sign the Paris accord for climate change on Friday. World leaders in December agreed to limit the rise in global temperature to “well below 2°Celsius (C)" over pre-industrial levels and to make efforts to limit it to 1.5°C over pre-industrial levels by 2100. But what difference can half a degree make across the world?

A new report published on Thursday in Earth System Dynamics, an open access journal of the European Geosciences Union, explains the difference that half a degree can make across the world.

The additional 0.5°C could mean a 10-cm-higher global sea-level rise by 2100, longer heat waves, and would result in nearly all tropical coral reefs being at risk.

The team, with researchers from Germany, Switzerland, Austria and the Netherlands, identified a number of hot spots around the globe where projected climate impacts at 2°C are much more severe than at 1.5°C.

They considered 11 different indicators including extreme weather events, water availability, crop yields, coral reef degradation and sea-level rise. Here are some highlights from their findings:

Mediterranean region: Already facing climate change-induced drying, a global temperature increase of 1.5°C will reduce the availability of fresh water in the region by 10% as compared to the late 20th century. In a 2°C world, the researchers project this reduction to double to about 20%.

Tropical regions: A global temperature rise of 1.5°C could adversely impact crop yields, particularly in Central America and West Africa. On average, local tropical maize and wheat yields would reduce twice as much at 2°C compared to a 1.5°C temperature increase, the study suggested. In tropical regions, warm spells will last up to 50% longer in a 2°C world than at 1.5°C.

Coral reefs: Limiting warming to 1.5°C could provide tropical coral reefs scope to adapt to climate change, but a 2°C temperature increase by 2100 would put nearly all of these ecosystems “at risk of severe degradation due to coral bleaching".

Sea level rise: On a global scale, a sea level rise of about 50 cm by 2100 in a 2°C warmer world can be expected, which is 10 cm more than for 1.5°C warming. “Sea level rise will slow down during the 21st century only under a 1.5°C scenario," explains lead author Carl Schleussner, a scientific advisor at Climate Analytics in Germany.