Headlines related to recent extreme weather appear to come out of a science fiction book: Even the richest countries in the world can’t control widespread fires — they’re even burning in the Arctic. Deadly flooding in Germany and Belgium in July 2021 completely washed away buildings and cars, and more than 1,000 people remain missing. Hundreds died in flooding in China. The U.S. Pacific Northwest, known for its cool climate, hit over 100 degrees F for several days. And the Arctic lost an area of sea ice equivalent to the size of Florida between June and mid-July 2021.
These changes are happening with average warming of just 1.1 degrees C (1.98 degrees F) over pre-industrial levels. The newest report from the Intergovernmental Panel on Climate Change (IPCC), world’s most authoritative body on climate science, finds that this is just a taste of what’s to come.
The IPCC Working Group I sixth assessment report shows that the world will probably reach or exceed 1.5 degrees C (2.7 degrees F) of warming within just the next two decades. Whether we limit warming to this level and prevent the most severe climate impacts depends on actions taken this decade.
Only with ambitious emissions cuts can the world keep global temperature rise to 1.5 degrees C, the limit scientists say is necessary for preventing the worst climate impacts. Under a high-emissions scenario, the IPCC finds the world may warm by 3.3-5.7 degrees C (5.9-10.3 degrees F) by 2100 — with catastrophic results.
Of course, every fraction of a degree of warming comes with more dangerous and costly consequences. In just a decade’s time, we’ll be looking back on today’s apocalyptic headlines thinking how stable things were back in 2021.
The report offers policymakers a clear-eyed view of the current state of global climate change and lays out the transformational action governments must take to avoid a calamitous future. Here are five things you need to know:
1) We’re on course to reach 1.5 degrees C of warming within the next two decades.
In the scenarios studied by the IPCC, there is a more than 50% chance that the 1.5 degrees C target is reached or crossed between 2021 and 2040 (with a central estimate of the early 2030s). Under a high-emissions scenario, the world reaches the 1.5 degrees C threshold even more quickly (2018-2037).
If the world takes a carbon-intensive pathway (SSP5-8.5), global warming could climb to 3.3-5.7 degrees C (5.9-10.3 degrees F) higher than pre-industrial levels by the end of the century. To put that in perspective, the world has not experienced global warming of more than 2.5 degrees C (4.5 degrees F) for more than 3 million years, a period with a very different climate system.
At the same time, the report shows that even with stringent emissions-reduction measures, we have already baked a lot of warming into the climate system. We are guaranteed to face more dangerous and destructive extreme weather events than we are seeing today, underscoring the need to invest much more in building resilience.
2) Limiting global warming to 1.5 degrees C by the end of the century is still within reach, but requires transformational change.
On the other hand, if the world takes very ambitious action to curb emissions in the 2020s, we can still limit warming to 1.5 degrees C by the end of the century. This scenario includes a potential overshoot of 1.6 degrees C between 2041 and 2060, after which temperatures then drop below 1.5 degrees C by the end of the century.
Small-scale efforts won’t be sufficient; we’ll need rapid, transformational change.
The world’s remaining carbon budget — the total amount we can emit and still have a likely chance of limiting warming to 1.5 degrees C — is only 400 gigatonnes of carbon dioxide (GtCO2) as of the beginning of 2020 (a figure which can vary by 220 GtCO2 or more if you factor in action on non-CO2 emissions such as methane). Assuming recent global emissions levels of 36.4 GtCO2 per year, this amounts to about 10 years before we exhaust the budget. While global emissions dipped due to COVID-19, they have bounced back quickly.
We must redefine the way in which we use and produce energy, make and consume goods and services, and manage our land. Limiting the dangerous effects of climate change requires the world to reach net-zero CO2 emissions and make major cuts in non-CO2 gases like methane. Carbon removal can help compensate for harder-to-abate emissions, such as through natural approaches like planting trees or technological approaches like direct air capture and storage. However, the IPCC notes that the climate system will not immediately respond to carbon removal. Some impacts, such as sea level rise, will not be reversible for at least several centuries even after emissions fall.
While achieving the 1.5 degrees C target will be difficult and will require managing trade-offs, it also provides a massive opportunity: Transformation can lead to better-quality jobs, health benefits and livelihoods. Governments, corporations and other actors are slowly recognizing these benefits, but we need greater, faster action.
3) Our understanding of climate science — including the link to extreme weather — is stronger than ever.
It is now unequivocal that human-caused emissions, such as from burning fossil fuels and cutting down trees, are responsible for recent warming. Of the 1.1 degrees C of warming we’ve seen since the pre-industrial era, the IPCC finds that less than 0.1 degrees C is due to natural forcings, such as volcanos or variations in the sun.