Half A Degree Makes Huge Difference In Global Warming

According to European researchers the impact of global warming on climate change is radically different even with half a degree of difference.

The climate change impacts for global warming of 1.5 degrees Celsius and 2 degrees Celsius by 2100 are substantially different, according to a new study. Those two temperature limits were included in the Paris climate agreement, says the paper, published in the journal Science.

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Global warming a real threat to many areas of the world

With an additional temperature rise of just 0.5 C we would see a further 10 centimeter increase in global sea levels by 2100, longer heat waves, and threats to almost all tropical coral reefs. The full results of the study are published in Earth System Dynamics.

“We found significant differences for all the impacts we considered,” says the study’s lead author Carl Schleussner, a scientific advisor at Climate Analytics in Germany. “We analysed the climate models used in the [Intergovernmental Panel on Climate Change (IPCC)] Fifth Assessment Report, focusing on the projected impacts at 1.5°C and 2°C warming at the regional level. We considered 11 different indicators including extreme weather events, water availability, crop yields, coral reef degradation and sea-level rise.”

Researchers from Germany, Switzerland, Austria and the Netherlands made up the team which identified a number of areas around the world in which impacts would be much greater at 2 C than 1.5 C. One such area is the Mediterranean, which is drying out due to climate change.

Tropical regions set to suffer most

If temperatures rise by 1.5 C, the availability of fresh water in the Mediterranean would drop by 10% compared to the late 20th century. However if there is a 2 C rise, that figure would reach 20%.

Tropical regions such as Central America and West Africa would see a big difference in crop yields due to global warming. Maize and wheat yields would drop by twice as much in a 2 C world as in a 1.5 C world.

In fact tropical regions stand to suffer the most if there is a further 0.5 C rise in temperatures, and warm spells would last up to 50% as long. “For heat-related extremes, the additional 0.5°C increase marks the difference between events at the upper limit of present-day natural variability and a new climate regime, particularly in tropical regions,” explains Schleussner.

Tropical coral reefs could also be affected by global warming. While a 1.5 C rise would allow coral reefs to adapt to climate change, a 2 C rise would leave almost all of these environments at risk due to coral bleaching, which can cause severe degradation.

Huge rise in impacts with just 0.5 C difference

The scientists believe that sea levels will rise by 50 centimeters by 2100 in a 2 C world, an increase of 10% over the 1.5 C equivalent. “Sea level rise will slow down during the 21st century only under a 1.5°C scenario,” explains Schleussner.

Co-author Jacob Schewe, of the Potsdam Institute for Climate Impact Research in Germany, says: “Some researchers have argued that there is little difference in climate change impacts between 1.5°C and 2°C. Indeed, it is necessary to account for natural variability, model uncertainties, and other factors that can obscure the picture. We did that in our study, and by focusing on key indicators at the regional level, we clearly show that there are significant differences in impacts between 1.5°C and 2°C.”

William Hare, a senior scientist and CEO at Climate Analytics who also took part in the Earth System Dynamics research, adds: “Our study shows that tropical regions – mostly developing countries that are already highly vulnerable to climate change – face the biggest rise in impacts between 1.5°C and 2°C.”

“Our results add to a growing body of evidence showing that climate risks occur at lower levels than previously thought. It provides scientific evidence to support the call by vulnerable countries, such as the Least Developed Countries and Small Island Developing States, that a 1.5°C warming limit would substantially reduce the impacts of climate change,” says Hare.