World leaders, decision makers and climate scientists in Egypt are currently
locked into the latest round of tense negotiations to address climate
change at COP27.
There is an urgent ambition to keep global temperature rise at or below
1.5°C to avoid the most dangerous impacts of climate change.
But what does that mean?
Well, it was an aim agreed at the Paris Climate Conference in 2015
to limit global temperature rise to 1.5°C when compared
with the time before the Industrial Revolution.
That was when humanity started to burn a lot of coal and other fossil
fuels emitting carbon, which, as we know, warms the atmosphere.
The rise since those times is already above 1°C and
rising, so we only have a short window to put in place reductions
of carbon emissions if we are to meet that main goal.
The impacts of climate change are already being felt and above 1.5°C the
impacts become more difficult to deal with.
More people being dangerously affected and damaging effects to infrastructure
and nature. And there is also a greater risk of irreversible changes.
So where are we now and how realistic is the ambition?
Well, along the bottom of this graph, we have emissions, the amount
of carbon dioxide and other greenhouse gases we expect to
put into the atmosphere in the year 2030.
And this grey bar shows the cuts in carbon emissions by
2030 that were agreed by the nations at last year's COP26
climate conference in Glasgow.
One estimate of these pledges, they're known as Nationally Determined Contributions
or NDC's, would take 2030 emissions into
the range of 45 to 49 gigatonnes.
A gigatonne is a billion tonnes or a thousand million tonnes.
If these obligations were met by 2030, well, what
is the likely impact on global temperatures?
Let's see.
By running climate models many, many times, we can produce projections
of how the global temperature will change over the rest of this century.
Each of these hundreds of dots represents the peak temperature
of a plausible projection to achieve a global temperature change
of 1.5°C or below by the year 2100.
The Y axis here is showing the highest temperature we would see
during the century. In each of these projections.
It's worth noting here there are a lot of other projections where we don't get back
to 1.5°C by the end of the century.
But we're focussing here on the outcomes that can hit that aim.
Now, some such as these show that global temperatures
could climb above 1.8°C, or overshoot,
before coming back down to 1.5°C by the end of the century.
But others, such as these over here show that global
temperatures may not go above 1.5°C, allowing us to stave off
the worst impacts of climate change.
Let's take a look at the current pledges, because in this grey line here, there
are no dots or projections which keep us below 1.5°C
throughout the century without at some points the so-called overshoot.
However, now look at what happens if we slide or
increase the level of ambition to the left and reduce
climate emissions.
We start to see projections under the 1.5°C,
showing that the worst impacts of climate change can be averted with
increased ambition.
And this is what the negotiations are all about.
The further humanity can move this pledge bar to the left, the
more that can be done to protect, well, humanity.
We'll need to see at the end of negotiations this week just how far world
leaders have been able to shift the bar on this one.
There is a slight catch here.
However, there are many more dots still above that 1.5°C
line indicating there are more projections with overshoot, even with
all this ambition.
So there are two difficult issues to resolve: large emission reductions
are needed to continue beyond 2030; and we also
need to physically remove carbon from the atmosphere after 2030.
So, can society develop the technology to suck out
the excess carbon dioxide from the atmosphere by 2100
to bring global temperatures back down again?
Technology to capture carbon and store it is yet to be proven
at the scale needed to lower global temperatures.
This means that the chances of returning to 1.5°C seem more
remote.
So in summary, it is possible to keep temperatures to 1.5°C
and more ambition will not only keep the worst extremes of climate change at bay...
...but will also mean there is less reliance on developing new technologies.