Why are 1.5 degrees and 2030 so important?
Given the fact that we are experiencing global warming due to human emissions of greenhouse gases, it is important to ask the question: how much global warming is safe?
For most of the last few decades it was argued that as long as global temperatures did not rise above 2C life could pretty much go on as normal. A rise in global temperatures above 2C, however, was considered to pose a serious threat to the continuance of human civilisation as we know it, as well as the stability of the earth's climate and biodiversity. This was due to the presence of feedback loops within the earth's climate system, often referred to as 'tipping points', which are increasingly likely to be triggered once a certain temperature threshold has been reached.
Over the last 15 years however, as the science of climate change has developed and the impacts become clearer, this threshold has been lowered to 1.5C, with 2C being described as 'a death sentence' by some scientists. The reasons why 1.5C are so important, and what the consequences of failing to respect this threshold, are outlined in the IPCC sixth assessment report [1].
The report makes clear that 1.5C is not a magic threshold, but that there is a sliding scale of risk, and that the risks associated with climate change are lower at 1.5C than at 2C, and which in turn is lower than the risks at 2.5C, and so on.
However, even at 1.5C, there is still a 50-50 chance of triggering a tipping point in the climate system and of having it run out of control, so 1.5C is not a 'safe' level of climate change, as there is no safe level of climate change. As temperatures climb higher than 1.5C the odds of triggering runaway global warming become more likely than not. So 1.5C represents a threshold beyond which the science suggests that it is more likely than not that runaway global warming will be triggered. Once runaway global warming is triggered, there is nothing we can do to stop it.
Why 2030 is Important?
In the sixth assessment report the IPCC has modeled various pathways that humanity can travel along that will keep climate change below the 1.5C limit. What those pathways all have in common is that they require a 25-45% reduction in emissions from 2010 levels by 2030, and for the world to reach net zero emissions by 2050.
Many scientists think that limiting warming to 1.5C is no longer possible, and that the world has already committed itself to overshoot. The latest scientific analysis [2] however shows that achieving the 1.5C limit is still possible, but that it would require very strong and immediate measures: the phasing out of all fossil fuels, the halving of CO2 emissions by 2030, and reducing emissions to net zero by 2050.
This is what makes the roadmap for humanity outlined at the Paris agreement of 2015, or the International Energy Agency's Net Zero 2050 roadmap [3] outlined at the 2021 COP in Glasgow so vitally important, as they remain humanity's best hope for averting catastrophic climate change.