Hello and welcome to this perhaps seminal blog on methane.
Although it may be easy to dismiss Peer Simon's suggestion about flatulence caused by baked beans as being completely ridiculous his attempt to bring the public's attention to the role of flatulance, and in the broader sense, the role of methane as a contributor to climate change perhaps is not as ridiculous as it first sounds!
To many 'Methane' may just conjure up associations of a dodgy smell, for others perhaps too they may think of its use as a common gas used for heating and cooking. There are others though who preach of its importance in arena of global warming and to its grave suggested global warming potential in the near future.
Blogging is a first for me and please bear this in mind in the first formative few weeks as I find my feet... Alright! So... It's an odourless gas and a hydrocarbon fuel but what other basics do we need to know before we get started? It's composition maybe? Methane is a simple hydrocarbon; it comprises of one carbon atom bonded to four hydrogen atoms. The smell commonly associated with it comes from other gases often accompanying it in gas supplies.
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| BBC, April 2014 |
To many 'Methane' may just conjure up associations of a dodgy smell, for others perhaps too they may think of its use as a common gas used for heating and cooking. There are others though who preach of its importance in arena of global warming and to its grave suggested global warming potential in the near future.
This is a blog investigating the significance of methane in the atmosphere and its influence on environmental change today and into the future.
Blogging is a first for me and please bear this in mind in the first formative few weeks as I find my feet... Alright! So... It's an odourless gas and a hydrocarbon fuel but what other basics do we need to know before we get started? It's composition maybe? Methane is a simple hydrocarbon; it comprises of one carbon atom bonded to four hydrogen atoms. The smell commonly associated with it comes from other gases often accompanying it in gas supplies.
Is it really a big deal though? Is it an important GHG? Is this a substantiable claim? (and a worthwhile topic for a blog!?). Well, we will find out. False assumptions will be quashed, statistics scrutinised and the real truth about Methane as a GHG unearthed over the coming months.
Methane is a less dense gas than air meaning if it is released into the atmosphere at surface level it is likely to make its way up into the upper atmosphere where the air is thin and water vapour levels low. It is likely to persist there for about 12 years, a period much less it should be noted than the (open to debate) atmospheric residence time of 'rival GHG' CO2. Over these 12 years though its ability as a gas to absorb solar radiation far outstrips CO2 as it can be said to be about 100 times more powerful a GHG than CO2 on a pound for pound basis.
Methane is a less dense gas than air meaning if it is released into the atmosphere at surface level it is likely to make its way up into the upper atmosphere where the air is thin and water vapour levels low. It is likely to persist there for about 12 years, a period much less it should be noted than the (open to debate) atmospheric residence time of 'rival GHG' CO2. Over these 12 years though its ability as a gas to absorb solar radiation far outstrips CO2 as it can be said to be about 100 times more powerful a GHG than CO2 on a pound for pound basis.
Statistics like this sounds quite grave really but surely there's not much of it to make a big impact, is there? It's all about CO2 in the grand scheme of things is it not?
Sam Carana, 2013
Well... Figures such as these highlighting the recent changes in atmospheric concentration of CO2 and of methane over the past 400,000 years suggest perhaps methane is due some more attention in light of atmospheric changes seen since the rise of man as the dominant species on earth. When CO2 is running at about 65% above its mean level for the past 400,000 years methane is currently running at a level 230% above its mean level from the last 400,000 years.
Clearly today's levels are unprecedented for many hundreds of thousands of years but the extent of variance from the historical mean is 3.5 times greater for methane than it is for CO2 and a contributing reason for the focus of this blog as methane's significance as a major GHG continues to rise.
IPCC AR5, 2013
Clearly today's levels are unprecedented for many hundreds of thousands of years but the extent of variance from the historical mean is 3.5 times greater for methane than it is for CO2 and a contributing reason for the focus of this blog as methane's significance as a major GHG continues to rise.
Let's take a look at following figure to consider its recent increases a little further:
Although both CO2 and methane are clearly rising fast the level of methane can be said to have been at approximately 1,800 parts per billion in 2000. Studying the CO2 figure, for fair comparison, it could be said that in 2000 the CO2 level was at about 370 parts per million, or 370,000 per billion. In 2000 it could hence be said that atmospheric CO2 concentrations were about 200 times greater than atmospheric methane levels, which is a number regularly cited when comparing relative atmospheric presences today.
Considering this ratio of 1-200 and that methane is 100 times more a powerful GHG than CO2 it can easily be seen that methane's radiative forcing contribution is about 50% as great of that of CO2's. In fact, it is even more significant than this, according to the IPCC AR5 report the RF of CO2 today when published in 2013 was 1.82W/m2, for methane it was said to be 0.97W/m2 - 53% as great as the radiative forcing resulting from atmospheric CO2.
Clearly then methane is an important GHG and as the lesser discussed sibling as the perennially discussed CO2 it will form the focus of this blog going forward in the coming weeks.
Clearly then methane is an important GHG and as the lesser discussed sibling as the perennially discussed CO2 it will form the focus of this blog going forward in the coming weeks.
I hope you enjoy reading and following the developments over this time and consider following my blog/engaging below on any topics, if you wish to.
Good start Robert. You should always cite the various facts and figures by hyperlinking test to relevant sources. For example, you state the CH4 is 100 times more powerful GHG than CO2, but according to the info I've read, this is too high, and the figure should be c. 21 times. It's worth mentioning as well sources of methane from farming and wetlands....
ReplyDeleteThanks Anson for the headers - will take those on board fully hereafter.
ReplyDeleteThat's a really interesting and valid point you raise and one I was hoping to focus on a little more next week, and in future weeks, as it requires further discussion on this blog (and potentially elsewhere too in the discipline…)
Without wanting to completely spoil next week’s blog:
The '100 times more powerful' mention was in relation to a mention in a paper I read focusing on Methane’s ability to warm on a physical, instantaneous basis; not considering how this diminishes over the passage of time. You’re completely right; methane’s GWP (Greenhouse Warming Potential) is often cited as 21 times that of CO2 when looking at a 100 year horizon.
Its ability to warm and hence the gas’s net contribution to global warming though I believe may be being masked somewhat by the time horizons publishing bodies choose to cite. I think it’s easy to think about the small scale - what emitting Xkg of methane will do on X,Y and Z timeframes but I think the shortfall of GWP statistics is the risk of missing the bigger picture…
I’ll try and elaborate on this using an example which should substantiate the figures mentioned in my blog: The United Nations Framework Convention on Climate Change choose to cite GWP of their study GHGs only on 20, 100 and 500 year time horizons (for which their figures are 56, 21 and 6.5 respectively).
If the 20 year GWP figure and the understanding that methane resides for just 12 years are considered the physical ability of methane to warm can be inferred relatively easily to be near to the figure of ‘100 times the power of CO2’ that was mentioned in the blog;
(Working with the UNFCC data already mentioned)
-12 years as proportion of 20 years is 0.6
-20 year horizon GWP of methane is 56
-56 / 0.6 is 93.3
I hope though that explains where the ‘100 times as powerful’ figure came from, I should have elaborated what exactly it referred to in more detail when writing the introductory post. Will do in the future.
Taking this approximate calculation forward my later suggestion that methane is responsible for 50% of the radiative forcing CO2 contributes holds quite well against the findings of the IPCC AR5 report which suggests methane contributes to a less conservative but broadly similar figure of 57% as much radiative forcing as CO2 presently does.
Maybe I’m barking up the wrong tree in focusing solely on methane… perhaps though it will expose the lesser discussed impacts of the agricultural industry? Or the byproduct of ongoing, large scale, land use change? Or a side-effect of a warming climate and perma-frost becoming not so perma-frost…?
These will all be considered in coming weeks, as too will the future for the gas.
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For those curious to think more about this before future blogs are published maybe have a think about the trends in atmospheric prevalence of CO2 and methane since the advent of the industrial revolution:
In 1800 atmospheric methane levels were at c. 750ppbv, today they are at c. 1,840ppbv
[Increase: 145%]
In 1800 atmospheric CO2 levels were at c. 280ppm, today they are at c. 400ppm
[Increase: 42%]
Does CO2 deserve its label as the runaway GHG?