Landmark report underscores urgent climate change challenge

By Mark Lynas

October 8, 2018

A landmark United Nations scientific report released today makes clear the enormous magnitude of the climate change challenge currently facing humanity.

The report paints a bleak picture of the ramifications of failing to control global warming, including increased human diseases, hunger and poverty, major ecosystem disruptions and more extreme weather events.

The world has already warmed by 1 degree Celsius since pre-industrial times and limiting global warming to 1.5C would require “rapid, far-reaching and unprecedented changes to all aspects of society,” warns the UN Intergovernmental Panel on Climate Change (IPCC).

Governments agreed in Paris in 2015 to “pursue efforts” to limit the temperature rise to 1.5C, a stronger target than the 2C previously advocated. The Paris Agreement tasked the IPCC with exploring the scientific details of how 1.5C might differ from the 2-degree target.

Today’s report reveals that meeting the 1.5 target would require carbon emissions to fall by 45 percent by 2030 and reach “net zero” by 2050. Emissions would also have to become negative for the second half of the 21stcentury, using questionable technologies yet to be developed at scale.

“Limiting warming to 1.5ºC is possible within the laws of chemistry and physics but doing so would require unprecedented changes,” said Jim Skea, co-chair of IPCC Working Group III.

However, if emissions are not constrained and global warming continues at its current rate, the planet will pass the 1.5C target sometime between 2030 and 2052. Separate analyses have shown that current carbon mitigation pledges are likely insufficient to avoid a catastrophic 3- to 4-degree warming.

The current anti-science and populist political mood threatens to undermine even the modest targets agreed in Paris. US President Trump has pulled America out of the Paris Agreement and pledged to revive the moribund coal industry.

Australia has also effectively ditched Paris, and the leading presidential candidate in Brazil, Jair Bolsonaro, has also rejected his country’s Paris commitments and pledged to accelerate the destruction of the Amazon rainforest.

The full IPCC report outlines in detail the additional impacts expected in a 2C warmer world as compared to a 1.5C target. These include more extreme weather, longer and more frequent droughts and heatwaves, and a higher rate of sea level rise.

Impacts on ecosystems and biodiversity will also be worsened by additional warming. While 6 percent of insects, 8 percent of plants and 4 percent of vertebrates stand to lose over half of their climatically suitable range for 1.5C warming, this rises to 18 percent of insects, 16 percent of plants and 8 percent of vertebrates for a 2C warmer planet.

With 1.5C of warming, more of the Arctic Ocean ice cap is expected to remain. With 2C, the IPCC projects the Arctic will become ice-free in summer at least once every decade.

Perhaps the grimmest ecological projection is for tropical coral reefs. Reefs are already suffering bleaching events due to rising sea surface temperatures, and a further loss of 70 to 90 percent is projected with 1.5C of warming.

However, more than 99 percent of coral reefs are projected to disappear with 2C of warming, meaning a virtual extinction of the tropical coral ecosystem worldwide.

The IPCC report also outlines risks to humans, especially people living in vulnerable and developing countries. The report’s summary concludes:

“Poverty and disadvantages are expected to increase in some populations as global warming increases; limiting global warming to 1.5°C, compared with 2°C, could reduce the number of people both exposed to climate-related risks and susceptible to poverty by up to several hundred million by 2050.”

Some of the increasing risks include rising death tolls from heat-related stress and the spread of vector-borne diseases such as malaria and dengue fever.

There are also risks of losses of food production for the higher global warming scenarios. The IPCC states:

“Limiting warming to 1.5°C, compared with 2°C, is projected to result in smaller net reductions in yields of maize, rice, wheat, and potentially other cereal crops, particularly in sub-Saharan Africa, Southeast Asia, and Central and South America.”

The full report makes clear that dietary shifts away from a reliance on livestock — especially ruminants like cattle and sheep — and towards plant-based diets could contribute as much as 20 percent of the total mitigation effort needed to hold warming below 2C.

The IPCC also backs biotech as a potential “climate smart” option in making world farming more sustainable and improving food security in developing countries.

It states that “genome editing tools may moderately assist in mitigation and adaptation of agriculture in relation to climate changes, CO2 elevation, drought and flooding” and that biotechnology “could contribute to developing new plant varieties that can adapt to warming of 1.5°C.”

However, with anti-GMO groups across sub-Saharan Africa and elsewhere mobilizing to stop farmers from accessing drought-tolerant and pesticide-reducing crops, the scientists recognize that political barriers remain a serious challenge.

“However, biosafety concerns and government regulatory systems can be a major barrier to the use of these tools as this increases the time and cost of turning scientific discoveries into ready applicable technologies,” the IPCC writes.

None of the emissions pathways assessed by the IPCC succeed in keeping the planet’s temperature below 1.5C unless “negative emissions” are used to draw down excess CO2 from the Earth’s atmosphere.

The IPCC points out that negative emissions would require millions of square kilometres of farmland to be converted to energy crops or forest regrowth, and that this may have potentially negative impacts on food security unless it can be combined with dietary shifts towards plant-based diets and “sustainable intensification” of agriculture.

“1.5°C and 2°C modelled pathways often rely on the deployment of large-scale land-related measures like afforestation and bioenergy supply, which, if poorly managed, can compete with food production and hence raise food security concerns,” the scientists write.

Ninety-one authors and review editors from 40 countries prepared the IPCC report, which is based on an assessment of more than 6,000 peer-reviewed papers from the scientific literature.

Overall, the IPCC assessment makes clear that achieving a 1.5C target remains physically possible – though just barely. Whether it is politically possible, however, seems much more doubtful.