It is now though time to reflect on all that we have touched on and to form 10 concise, take-away conclusions and lessons learned...
My 10 key points to take away for the future!
1. Today Methane is the 2nd most significant GHG, it is presently responsible for 53% as much radiative forcing as CO2 provides
Here we go...
2. Methane's ability as a GHG is many times stronger than CO2 (about 120 times as great) yet its residence time is significantly shorter - at present thought to be about 12 years. This means warming from methane is much sharper, yet shorter lived than warming from CO2.
3. Methane's GWP has been significantly raised since it was first cited as having a 100 year GWP of 21 in AR2. Despite the fact this number is significantly erroneous it is still widely utilised today, including in emissions trading schemes.
4. Today we contribute 330Tg/year of anthropogenically produced methane to the atmosphere. It is thought natural production is about 280Tg/year, unsurprisingly methane levels have risen significantly since the rise of man and are now at their highest level for at least 800,000 years.
5. Of this anthropogenic methane emission 50% is created by agriculture
6. There is now 1,800ppb methane in the atmosphere, about 1/200th of the amount of CO2 that there is. CO2's growth rate of 60% compared to pre-industrial times is insignificant compared to methane's standing at 150%. Despite a pause in growth methane's growth appears to have accelerated again significantly in the past few years.
7. 90% of methane is metabolised by the unusual OH radical which is an important agent in breaking down other GHGs too. It has sensitive requirements for its creation that limit its rate of production. Measuring the abundance of this molecule in the atmosphere is hard, despite this it is thought though that its abundance could be in decline.
8. If OH levels are becoming depleted this means the residence time of methane is increasing. This could have significant consequences for the GWP of methane.
9. Scientists are keen to draw parallels between the global warming being experienced today, and for the coming decades to past warming events to try to predict the responsiveness of the earth's methane stores to a warming climate.
10. Methane hydrates and permafrost are though to pose the largest risks for the future. Knowledge into the stores is limited though and the many reports contradicting of each other. Despite this the current academic consensus is that rapid, large scale methane releases are unlikely in coming decades however could take place in the future if predicted potential global warming paths are realised.
There we are! 14 weeks, 14 posts and 7,200 thousand words of analysis, critique and comment later we have arrived at the end of our journey! For those that have followed me throughout this project I hope you've learned as much as I have. Thank you too for those who have got involved; I've enjoyed our discussions on different matters along the way!
Very best,
Rob
A word cloud image; the size of a word indicates its frequency of use in the blog
(Graphic courtesy of worditout.com)
Didn't realise this was such a big issue. Thanks for getting this out there.
ReplyDeleteThanks Harri, thanks for following.
ReplyDeleteInteresting read! Is the modern diet a large contributing factor to this? Would a reduction of livestock farming by a change of diet make a big difference?
ReplyDelete