During a recent visit to the Natural History Museum, I was reminded that the carbon cycle is a natural phenomenon (bear with me, I am not turning sceptic on you). Carbon is stored in rocks, the ocean and living organisms. It is released into the atmosphere, for example as carbon dioxide or methane released by humans and animals, by forest fires and volcanic eruptions. It is then re-captured, for example by plants.

Climate change is also a natural phenomenon, however, we have sped up the release of carbon so much that the change is happening much quicker than it would have done naturally. Carbon dioxide absorbs heat and also radiates it, including back onto the earth's surface. As such, the more carbon dioxide in the atmosphere, the hotter the earth gets. 

There has been a lot of commentary on how achieving net zero by carbon offsetting is misleading. I still believe that offsetting is no replacement for reducing emissions (more on that below), but perhaps it does hold a place in the solution. Part of carbon offsetting is carbon capture. This can be by natural means (such as planting more trees) or by extracting carbon from the air and either reusing it (for example in food manufacturing) or storing it underground.

There are potential issues with carbon capture (and this is why reducing emissions needs to remain our first line of defence):

• it is a high cost solution (particularly direct air capture);
• the carbon is stored underground, but getting it there is difficult - significant energy is required to compress and chill CO₂ and maintain high pressure and low temperatures throughout the pipelines - so it is a question of whether enough carbon can be captured to make that energy usage worthwhile;
• it is important to look at the long term consequences of storing carbon in this way – do we know how much damage it might cause to the areas in which it is stored? Might there be issues with it seeping or leaking out and causing areas of particularly high concentration?

Whilst not an excuse or short cut to allow us to maintain our throw away lifestyles, carbon capture may be a useful tool for (somewhat) replicating nature to reduce the carbon already in the atmosphere and offset unavoidable emissions.