I have been doing a lot of reading around global warming – partly from an academic perspective and in part for general interest. It really is a hot topic (pun intended) for our generation; you can’t seem to escape the news coverage on it, with climate change summits becoming quickly known for ruthless through the night debating for weeks on end. I wanted to write this post to just talk about some of the more interesting things I have come across. This is not going to be a full round up of what climate change is and how it occurs – for those not in the know there is a rigorous discussion provided by the UK government here.

I think the first thing that I enjoyed reading both on the government source and in the text I was set to read as part of my studies is the acknowledgement that global warming is occurring. Global warming has become an incredibly politically charged phrase with a huge amount of debate from a variety of stakeholders. This often leads it to look a little bit like a debate into if global warming is happening at all – which is unfair. Global warming is happening right now, any scientist would not in their right mind debate this fact. The thing which is causing all of the debate and the excitement is the extent to which this increased warming is anthropogenic.

I think one of the most startlingly misquoted facts with reference to global warming is that sea levels will rise because the ice will melt. Intuitively this does not ring too many alarm bells, sounds about right. But if you put your science hat on and think about it there are two types of ice on this planet. The ice which sits on land and the ice which sits on water (basically icebergs, but some expanses are huge). When an ice sits on water it is totally and utterly irrelevant that a large portion of it is out of the water. The fact is the ice has already displaced the water as much as it would if it were all to be turned to liquid – the melting of this type of ice will have no impact at all on the overall sea levels. If all the ice on land were to melt then yes – the sea levels would rise a LOT. But for the ice on land to melt we would need a rise in the surface temperature so high we would of had much more pressing problems first. Where is all the excitement coming from? It’s thermal expansion. As the temperature on Earth begins to rise, the water expands and that makes the sea levels rise. Why can’t the media tell people this? I find it patronising to hide the real reasons from the public – it’s only fair.

In my exploration of global warming I took a trip down memory lane and revisited the water cycle and the carbon cycle. I must admit – it was really really fun, and actually I learnt some new facts so not at all wasted time. The new facts I learnt were:

• The average water molecule will be in the ocean for 3,000 years before being transferred to another reservoir – not quite so dynamic!
• In fact the fate for ice and snow is even more boring. The average water molecule as ice will be in residence for 10,000 years. This, of course does not apply to the sleet that falls over London on a December evening – it’s an average.
• Moving on to carbon, I somewhat naively always considered humans and other organic beings as a fairly major source of carbon. We make up 0.001% of all carbon – and that’s shared with plants and animals.
• The average residence time of our organic carbon is 4.7 years… I mean I kind of knew this it’s just so fun to think about the fact that you literally are a new person in some way every day. When you see old friends, you really can say it’s a whole new you with a smile.
• 99.99% of the worlds carbon is held in rock – for these unlucky molecules the average residence time in the rock is 200,000,000 years. Somewhat humbling when I think of my probably 80 hopefully 100 years.

I suppose I don’t really have too much more to say with regard to global warming – except to encourage any scientists out there to read up on the facts. It was really refreshing to go back to basics and learn about something from a non-media source, because to be fair I only read about global warming in the news. It is such a great multi-disciplinary subject and there are many things we know so little about. For example – we know that increased water vapour in the air is a bad thing. Water vapour can absorb infrared radiation because of its ability to have its rotation increased, which it later re-radiates warming the surface. But at the same time more water vapour means more cloud cover. More cloud cover means more blocking of solar radiation. In turn clouds absorb and admit infrared radiation. In fact cloud feedback is one of the least understood parts of the global warming issue.

My final comments would be to express a hope that all the scientists reading this will spread the message that global warming is indeed exacerbated by humans. The present rate of warming is 0.5 degrees celsius per century – I know it does not sound much but the effect is massive and like nothing we have seen in a very long history. Furthermore increases of carbon dioxide correlate well with the increase in surface temperature which only really correlate with human activity. The models used to simulate global warming simply cannot get it right if the effects of human activity are left out. Models which only consider natural emissions predict a temperature far lower than it is.

Global warming is caused by humans – and it’s worth a little thought.