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The report, published today by the UN’s Intergovernmental Panel on Climate Change, said that crucial policies to reduce global warming must be in place by 2030 to avoid the worst. If emissions continue at the current rate, 1.5 degrees of warming could be reached between 2030 and 2052, and temperatures would continue to rise steeply, the IPCC authors said.
According to the United States National Oceanic and Atmospheric Administration, Earth has already warmed by nearly a degree since 1900 due to carbon emissions from industry, farming, heating, and transport. Stabilising global warming to 1.5 degrees above pre-industrial level is possible, the authors of the report said. But, they added, meeting the goal will depend entirely on the political will of all countries.
“But it also comes with some wishful thinking that the messages are being taken up by the public, by policymakers and by governments,”
The aim of the report was to follow up on the Paris Agreement, a set of targets to limit climate change signed at a UN summit in Paris, France, in 2015. Scientists have warned that, even if all pledges under the agreement are implemented, humans will still emit around 58 gigatonnes of CO2 in 2030, far beyond the 35gt needed to halt global warming at 1.5 degrees.
The report highlights a number of potential pathways to prevent further warming, including removing carbon from the atmosphere, phasing out coal and reducing food waste. "The preparation of this report […] was a benefit in itself,” said Hans-Otto Pörtner, an ecologist at Germany’s Alfred Wegener Institute, who chairs an IPCC working group. “But it also comes with some wishful thinking that the messages are being taken up by the public, by policymakers and by governments.”
The IPCC report pointed out that there would be significant differences between a 1.5 degree world and 2 degrees of global warming. Under a 2-degree scenario, the proportion of people exposed to heat waves at least once every five years would leap from 14 to 37 percent. This will increase ozone-related mortality and the spread of vector-borne diseases, such as malaria and dengue fever, the report warned.
Even under the 1.5-degree scenario, ocean fishing is expected to decline by 1.5 million tonnes a year. But this figure would double, were global mean temperatures to reach 2 degrees of additional warming, the report said.
However, the IPCC authors make it clear that some mitigation measures need to be carefully managed to avoid negative 'trade-offs'. “Any poorly designed policy is going to have unexpected consequences,” says Joyashree Roy, an economics researcher at Jadavpur University in India, who coordinated the report’s summary for policymakers. “For example, if we adopted bioenergy at massive scale, this may lead to competition for land, which in turn may cause food prices to spike.”
Niklas Höhne, a co-founder of the NewClimate Institute think tank in the Netherlands, said that many transformations have already happened on a small scale. “One example is renewable energy, that has developed much faster than people thought only five years ago,” he told SciDev.Net. “Right now, renewables are so cheap that are outpricing coal even in countries like India, where people always thought this would never happen.”
Höhne concedes that the 1.5 degree target by itself is an aspirational goal, but that striving for it keeps global leaders aware of the problem. “Whether we reach it or not,” he said, "is not the most important question."