By Gloria Dickie
LONDON (Reuters) – The U.N. climate science panel report released on Monday lays out several paths for greenhouse gas emissions that could limit climate change or, alternatively, see it spiral out of control.
Grouping 1,600 potential pathways within eight broad categories, the Intergovernmental Panel on Climate Change describes how different government policies and industrial activities would influence the rise in global temperatures up to 2100.
Here’s how to understand those options:
MOST OPTIMISTIC
Only two categories of pathways – dubbed “C1” and “C2” in the report – could keep the world to its 2015 Paris Agreement goal of limiting warming to within 1.5 degrees Celsius of preindustrial temperatures.
C1 pathways would mostly hold temperatures at that threshold, whereas C2 pathways envision a temporary overshoot up to about 1.7° C before dropping back down to about 1.4° C by century’s end — a situation that could still unleash irreversible impacts such as dead coral reefs.
The world would need to invest big in renewable energy and make dramatic cuts in greenhouse gas emissions in this decade, including a massive scale back in use of coal, oil and gas.
But that alone wouldn’t be enough. Some carbon dioxide (CO2) would also need to be removed from the atmosphere through increasing global forest cover as well as with nascent technologies such as direct air capture.
These pathways would see emissions peak by 2025, and net-zero CO2 emissions by 2060. Because global emissions have continued to rise since 2017, the report says that even these pathways may still fall short of delivering the 1.5° C goal.
MORE FEASIBLE
More-realistic “C3” and “C4” pathways could restrict warming to 2° C – but only if governments quickly enact and expand their current national climate plans.
Instead, global emissions are on track to hit 57 gigatonnes per year by 2030, rather than the roughly 53 gigatonnes envisioned in the pledges. If countries don’t move within this decade to realize their national climate plans, emissions would need to decline steeply after 2030 – by more than 1.4 gigatonnes every year – until 2050.
These paths envision net-zero for CO2 by 2085, but some could fail to reach net-zero for all greenhouse gas emissions in this century.
Noting that both immediate action and steep cuts after 2030 will be hard for many countries, the report says these paths would likely also need governments to pass policies that tamp down consumer demand for energy use, travel and meat consumption.
CURRENT TRACK
“C5” to “C7” pathways describe doing little beyond what’s planned as of today, and would see the average global temperature rise of 2.1° C to 3.5° C by 2100, and continue rising in the next century.
These mirror what national climate policies as of 2020 would achieve if not strengthened by 2030, with the world warming by about 3.2° C.
Most fail to reach net-zero by 2100. The C7 pathways, predicting severe warming of 3.5° C, see emissions levels continuing to rise through the century.
WORST CASE
In the worst case scenarios, described as “C8” pathways, the world warms more than 4° C beyond preindustrial temperatures. Emissions increase dramatically as current climate policies are reversed and low-carbon technologies such as renewable energy sources and electric vehicles are rolled back.
Reaching net-zero CO2 emissions in this century is out of the question. By 2050, the world is emitting roughly 88 gigatonnes of greenhouse gases, a 46% increase from 2019 levels.
(Reporting by Gloria Dickie; Editing by Katy Daigle, Lisa Shumaker and Susan Fenton)
