The urgency of action on climate change is complicated. On the one hand, the harm of inaction is real and increases every year. On the other hand, there is no such thing as ‘too late’. Plug in some numbers and you can define a corresponding deadline to achieve a goal, but we’re not dealing with an all-or-nothing proposition. There is a continuum of consequences, and our choices can always take us up a notch in the direction of ‘better’ or ‘worse’.
With that in mind, the latest report from the Intergovernmental Panel on Climate Change (IPCC) shows that the coming years represent a crucial opportunity for our hopes of limiting global warming to the benchmarks of 1.5°C or 2°C. Those numbers aren’t magic, but they make sense. First, they represent a brighter future than any larger number on the thermometer. Second, these are the goals that have long been the focus of international negotiations.
(Gig) a lot of work to do
The release is the third and final part of the 6th Assessment Report. The first two releases dealt with the natural science of a changing climate and the impacts of climate change. This one is about climate solutions colloquially referred to as “mitigation”. The release examines past and current greenhouse gas emissions, illuminating the path to eliminating emissions and stabilizing our planet’s climate.
There are clear signs of progress. Previous reports have been forced to describe future scenarios of massive emissions as “business-as-usual” continuations of current trends. This report says these scenarios no longer seem likely. Rapid declines in the cost of renewable energy have led, among other things, to accelerated growth in clean energy. Together with national commitments, this puts us on a trajectory of about 3°C by 2100 rather than the 4+°C world of a “burn every bit of carbon you can find” emissions scenario.
From there to a world that actually stops however, heating up at 2°C or 1.5°C is a big job. Emissions data from recent years has raised the possibility that we are near the peak of the emissions curve. That should be true. In scenarios where warming stops at about 1.5°C or 2°C, the report says, “Emissions are expected to peak between 2020 and before 2025 at the latest.” In other words, emissions should be about to start falling now.
And after the peak, the emissions must also be steep reject. For the 1.5°C limit, emissions should fall by more than 40 percent by 2030 and reach net zero by the 2050s. Meeting the 2°C limit isn’t much easier – we need to cut by more than 25 percent by 2030 and reach net zero by the 2070s.
Another way to visualize these changes is to imagine a remaining “budget” of emissions before the world exceeds a chosen limit. About 1,200 gigatons of CO2 would push us from where we are now to 2°C. Just 400 gigatons would push us to 1.5°C. For a sobering context, the world emitted about 410 gigatons in the 2010s alone†
