climate change science

The steep path to 1.5 degrees

At the Paris climate talks last December, the international community recommitted itself to keeping below two degrees of global warming, with a stretch goal of 1.5 degrees. We’ve already had one degree of warming, so 1.5 is a much tougher target. As I’ve mentioned before, the difference between the two is much bigger than the fractional increase in heat. Climate change does not progress in a nicely orderly and linear fashion. Incidences of extreme weather are likely to double between 1 and 1.5 degrees, and double again between 1.5 and 2.

For some parts of the world, that’s the difference between climate change that they can adapt to, and conditions that are unliveable. Cue the evacuation of low-lying islands, and a new crisis of climate migration. The impact on crop yields would be much more serious, and perhaps most striking – at 2 degrees we are likely to completely lose all the world’s coral reefs.

This new challenge has prompted a lot of new work. Much of the emissions modelling and national strategising has been done around 2 degrees, and scientists are catching up. There’s a major conference on 1.5 degrees in Oxford happening this week. The IPCC has commissioned a special report on the target, to be delivere in 2018.

Two things we do know about a 1.5 degree target: first, it’s a challenge that borders on the impossible. It would be incredibly challenging even if everyone was 100% committed, and it’s hard enough getting agreement and action on 2 degrees. Second, and closely related to point one, it will require us to think beyond the usual carbon-cutting ideas. To hit 1.5 degrees, we will have to actively remove carbon from the atmosphere.


As the graph above shows, even a full transition to a genuinely zero carbon economy by 2050 won’t be enough to stay within 1.5 degrees. There’s too much CO2 in the atmosphere already. On top of all the transition technologies that need to be rolled out, we will also need carbon removal technologies that can capture and store CO2.

That’s not something I’ve written about before in much detail, but options do exist. Carbon capture and storage is the best known, but there are others. As they are now rising in importance, I will profile some of them in a future posts.


  1. It’s certainly worth making the point that there are natural ways of soaking up carbon from the atmosphere. Increased forest cover, peat bogs etc. can act as ‘carbon sinks’ (sometimes also referred to as ‘negative emissions’).

    The problem is we’ll need to do this anyway just to get down to ‘net zero emissions’ as there are some emissions we just don’t foresee being able to eliminate. Could we restore enough natural landscapes to get us beyond net zero as per the graph and keep below 1.5 without the need for new technologies? I agree it looks highly doubtful.

    The second problem is that we’re currently moving in precisely the wrong direction in terms of global land use.

    An uphill challenge to say the least.

  2. Hi J – Hope you’ve seen the latest from Bill McKibben – [] ‘Zero: that’s the new number.’ (as well as Monbiot’s latest)

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