The authoritative new report by the Intergovernmental Panel on Climate Change sets the world a clear target: we must reduce emissions of greenhouse gases to net zero by the middle of this century to have a reasonable chance of limiting global warming to 1.5C.
Every government should read this report and recognise the clear choice we now have.
Accelerate the transition to clean and sustainable growth or suffer the mounting damage from sea level rise, floods and droughts that will severely hinder efforts to tackle poverty, raise living standards and improve prosperity.
The report, prepared by leading researchers from around the world, warns that the world has already warmed by about 1C since the middle of the 19th century, and could reach 1.5C at the current rate of warming before the middle of this century.
Human activities are currently emitting about 42bn tonnes of carbon dioxide every year, and at that rate the carbon budget – allowing us a 50-50 chance of keeping warming to 1.5C – would be exhausted within 20 years.
Even 1.5C of warming would have brutal consequences, according to the report. Poor people, in particular, would suffer as the threat of food and water shortages increase in some parts of the world.
But the report makes clear that allowing warming to reach 2C would create risks that any reasonable person would regard as deeply dangerous.
One of the report’s most stark statements is that “limiting global warming to 1.5C, compared with 2C, could reduce the number of people both exposed to climate-related risks and susceptible to poverty by up to several hundred million by 2050”.
However, the report also makes clear that the target of halting global warming at 1.5C could still be technically feasible, particularly if there is a strong and immediate response from governments.
The report recognises that the collective pledges by governments that were submitted before the Paris agreement was reached in 2015 are consistent with warming of 3C by the end of the century. By contrast, a path that would prevent a rise of much more than 1.5C would require annual emissions to fall by about 50% between now and 2030, and reach net zero by 2050.
We have to achieve these emissions reductions over a period when the world’s economy will experience a radical transformation. Global infrastructure will have more than doubled between 2015 and 2030. The global economy will have doubled within two decades or so if it continues to grow at about 3% each year on average. And the population living in cities, where most emissions occur, will likely double in the next four decades.
Hence the next 10 years will be absolutely crucial in determining what kind of world will exist in the decades beyond. If we act decisively, and innovate and invest wisely, we could both avoid the worst impacts of climate change and successfully achieve the sustainable development goals, as the IPCC report emphasises. If we do not, we face a world in which it will become increasingly difficult for us and future generations to thrive.
But we will also need greater international cooperation. The IPCC report is clear that we may not be able to limit warming to 1.5C without the need later in the century to remove carbon dioxide from the atmosphere. Although we can do this by expanding forests and other vegetation, we must also explore other options, including the development of carbon capture and storage.
While many green campaigners are opposed to this technology because they fear it could undermine the pressure on the fossil-fuel industry, we cannot afford to close it off as an option. A collective international effort is needed to speed up research, development and deployment of this area.
While it is clear that it is still technically feasible to limit warming to 1.5C, we will not succeed without strong political will and leadership. Governments should recognise both the great peril we face from poor choices or hesitation, and the enormous opportunity on offer from the rapid transition to a clean and sustainable economy.
Governments, companies and communities should embrace this transition: it is the growth story of the 21st century. Cities must be planned so that we can live, breathe and move freely in them. And we must reverse the degradation of our land, soils and forests so that they are more productive and absorb more carbon dioxide. All of this is both possible and extremely attractive, as the most recent report from the New Climate Economy, published last month, spells out.
We will see in the next two years whether governments have understood the message of this IPCC report as they revise their nationally determined contributions to the Paris agreement.
We have in our grasp the opportunity to choose a safer and more prosperous future.