Why zero carbon by 2050 may not be enough

 

For years now, climate scientists have been saying annual global carbon emissions need to level off by 2020 and fall sharply thereafter until it reaches zero by 2050. This is to give us a chance of avoiding catastrophic climate change.

But I get the impression that all world leaders have been hearing is “Do something by 2020, blah, blah, blah, reach zero by 2050”.

Certainly, there doesn’t seem to have been any attempt to level off emissions by 2020 (although Covid may have achieved that temporarily), there also seems to be no sense of urgency about cutting emissions sharply during the 2020’s (just more promises, and no action), but they do all agree they want net-zero by a distant 2050 (by which time they’ll all be retired or dead).

So, what if we do get to net-zero by 2050 somehow? Is that it? Job done, regardless of how we get there?

Not necessarily. Let me explain:

Look at the following graph. It attempts to show global carbon emissions from 1980 to 2050 in billions of tonnes. Up to 2020, it’s a simplified line based on actual emissions at the beginning of each decade (2020 is an estimate). Between 2030 and 2050, the line is based on what I believe the climate scientists say we need.

 

Now look at this second graph. It’s the same sort of thing but gives a potential scenario where the World takes a more leisurely pathway to net-zero.

 

What’s wrong with that? Plenty.

Let me overlay the two graphs:

The area shaded in yellow shows the difference between the two lines. Still wondering what the problem is? After all, we’re still reaching zero in 2050.

Okay, we’re agreed the lines are based on total CO2 emissions aren’t we? E.g. 19 billion tonnes in 1980, 22.5 in 1990, etc.

It follows that the area under each line in the first two graphs broadly represents the total CO2 emissions between 1980 and 2050. So the yellow shaded area represents a whole chunk of extra CO2 going into the atmosphere between 2020 and 2050 if the world’s leaders take a more laid-back approach.

But we’re still reaching zero by 2050, so that’s okay isn’t it? No.

You see, the line beyond 2020 in the first graph is based on what’s known as a “Carbon budget”. Scientists have worked out how much CO2 we can afford to add to the atmosphere before we risk catastrophic climate change. This is the total Carbon Budget. So they say we have to cut our 2020 emissions by half during the 2020’s to stay within this budget, and keep cutting as hard as we can until we reach zero by 2050.

So that yellow shaded area effectively breaks that carbon budget.

Get it? Because I don’t think the politicians do yet.