World put on notice over climate change
Policymakers should read the whole report as global warming threatens the lives and livelihoods of people around the world, and the future of our planet
Areport by the Intergovernmental Panel on Climate Change (IPCC) confirms the enormous wisdom that governments showed in Paris in December 2015, when they agreed to the goal of “pursuing efforts” to limit global warming to 1.5 degrees Celsius.
The report’s summary for policymakers paints a sobering picture of the potentially terrible impacts of allowing global mean surface temperature to rise by 2 degrees Celsius compared with pre-industrial levels: More extreme weather, sea level rise and ocean acidification, with detrimental effects on wildlife, crops, water availability and human health.
But the policymakers, or at least their aides, should make the effort to read the whole report.
Incredibly, the stark summary is still a relatively conservative assessment of the consequences that we might face if global warming does exceed 1.5 degrees Celsius.
The report by IPCC, a scientific and intergovernmental body under the auspices of the United Nations, is a comprehensive review of the published evidence painstakingly compiled by hundreds of authors and reviewers over the past two-and-ahalf years.
The summary of the report was approved line by line by governments, including the United States, Australia and Saudi Arabia, during long and intensive discussions last week in South Korea. It is written in matter-of-fact language, but it omits some of the biggest risks of climate change, which are described in the full text.
For instance, the summary indicates that warming of 2 degrees Celsius would have very damaging impacts on many parts of the world, but it does not mention the potential for human populations to migrate and be displaced as a result, leading to the possibility of war.
This is a risk that many governments around the world have already recognised, with climate change often highlighted in national security assessments as a “threat multiplier”, which could increase the chances of political instability and conflict.
Too many uncertainties
The summary also leaves out important information about so-called “tipping points” in the climate system, beyond which impacts become unstoppable, irreversible or accelerate. It acknowledges that the land-based ice sheets in Greenland and West Antarctica may be destabilised even by warming of 1.5 degrees Celsius, ensuring several metres of sea level rise over the coming centuries.
Yet, there is no mention of other important thresholds that might, for instance, halt the Gulf Stream in the Atlantic, or cause shifts in the occurrence of the monsoons in Africa and Asia.
It is not clear why such crucial information has been left out of the summary.
Perhaps the authors must have felt that there were too many uncertainties in our knowledge to be definitive.
However, the danger is that policymakers will assume the absence of these very significant risks from the summary means that researchers have assessed them to be unimportant or impossible.
Uncertainties are also evident in the summary assessment of the economics of climate change and the cost of doing something about it. It indicates that, to keep to the 1.5 degrees Celsius target, carbon prices would need to be three to four times higher than for 2 degrees Celsius. But on the overall investment required, it states: “The literature on total mitigation costs of 1.5 degrees Celsius mitigation pathways is limited and was not assessed in this report.”
The overwhelming conclusion any reasonable policymaker will reach from reading the IPCC summary report is that the target of keeping global warming to the level of 1.5 degrees Celsius is both affordable and absolutely necessary in order to avoid highly dangerous consequences for the planet.
The question now is whether world leaders such as United States President Donald Trump and Scott Morrison, the Prime Minister of Australia, will ignore the IPCC report and continue their policy of inaction on climate change, including a disregard of the Paris agreement, when the impacts so clearly threaten the lives and livelihoods of people in their countries and around the world. ■ Bob Ward is policy and communications director at the ESRC Centre for Climate Change Economics and Policy at the London School of Economics and Political Science.