Conclusions

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!

Here we go...

1. Today Methane is the 2nd most significant GHG, it is presently responsible for 53% as much radiative forcing as CO2 provides

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)

Risks for the future 2: Methane Hydrates

Methane Clathrates: the scare factor

Over the last decade there have been several publications citing methane hydrates(also known by methane clathrates) as being cause of utmost concern in the coming century, having even been nicknamed as the source of 'artic methane apocalypse or 'arctic methane catastrophe'. The Arctic Methane Emergency Group are certainly gravely concerned (http://ameg.me for more), the following taken from a summary of reasons for action needing to be taken immediately:

Source: Arctic Methane Emergency Group

There are clearly many big claims here, the last though has been the subject of intense debate over the past few years - the suggestion that 'a 50 gigaton methane burst is possible at any time'. 

(Source: Authors own)

As the figure above highlights - this really is a release of enormous scale and if it were to happen on anything but a multi century-scale timeframe would certainly have very major consequences for humanity. So, what are the chances of this happening and where does the figure of 50Gt come from?

Plume of methane from methane hydrates being emitted from ocean floor

Source: Ruppel (2011)

Well... It originally appeared in a short paper by Shakova et al. published in 2008 (full paper available here). Since then there has been intense to-ing and fro-ing in the scientific community with various skeptic groups trying to outprove the other as to the likelihood of a 50Gt release in particular, but also the chances of any significant release this century. If you're interested in learning more about this a summary article published by the Guardian is available here.

At present, I would conclude it remains hard to nail down a genuinely substantiable statistic as to the likelihood of a methane burst from stored hydrates. The conclusion by the IPCC in 2013 that:

Source: Carbon and Other Biogeochemical Cycles in IPCC AR5, 2013

Appears true today also - I struggled to find any new evidence since 2013 substantiating the likelihood of the burst any more solidly than prior to 2013. An article in the New Scientist (23 May 2015: p38-41) came to the same conclusion with their investigation which coined their front-cover headline "It's not grim up north - arctic safe from methane apocalypse" along with the concluding statement 

"There is, then, no solid evidence to back the idea of a methane bomb and past climate records suggest there is no cause for alarm."

For the sake of the planet and of mankind let's hope Anil Ananthaswamy from New Scientist is right on this one and that conclusions like hers and like Ruppel's (2011) are indeed correct; 

"Catastrophic, widespread dissociation of methane gas hydrates will not be triggered by continued climate warming at contemporary rates (0.2ºC per decade; IPCC 2007) over timescales of a few hundred years."

References:

Ananthaswamy, A. (2015). The methane apocalypse. New Scientist, pp.38-41.

Ciais, P., C. Sabine, G. Bala, L. Bopp, V. Brovkin, J. Canadell, A. Chhabra, R. DeFries, J. Galloway, M. Heimann, C. Jones, C. Le Quéré, R.B. Myneni, S. Piao and P. Thornton, 2013: Carbon and Other Biogeochemical Cycles. In: Cli- mate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 

Ruppel, C. D. (2011) Methane Hydrates and Contemporary Climate Change. Nature Education Knowledge 3(10):29

Risks for the future: Melting permafrost

First off... Melting permafrost and methane release

A changing climate and accelerated warming in polar regions is causing grounds traditionally held in a permafrost state to transition into a sporadically frozen or even fully defrosted state. 

Permafrost - The tipping time bomb

As the video above explains this enables the carbon rich organic matter held in the soil to continue its natural decomposition stalled for as long as it remains frozen. When this decomposition place in the absence of oxygen methane is produced. This can happen in big, explosive and very clear releases leaving craters on the landscape (as documented in this article from the Siberian times).

Methane explosion in Siberia

Source: Siberian Times

More commonly however it is an ongoing, discrete and gradual release of methane that is detectable via analysis of air compositions such as displayed in the following product from NOAA clearly showing high emissions from Siberia in this animation of methane levels in August 2007.

Source: Carbon Tracker-CH4 (available here)

The potential risks to permafrost defrosting and the subsequent methane production is undeniably massive if it were to happen on a significant scale. This is due to the enormous store of carbon held in permafrost, thought to be in the region of about 1,700GT. 

What continues to be the focus of debate is the chance of a major, rapid methane release occurring from the defrosting of permafrost and hence also, what climatic changes are needed to induce such a change. Some academics have suggested that the chance of a significant permafrost melting soon is quite likely. A paper titled 'Speleothems reveal 500,000 year history of Siberian Permafrost' by Vaks et al. (2013) used dating of "periods of speleothem growth in a north-south transect of caves in Siberia to reconstruct the history of permafrost in past climate states" their resounding conclusion is that "global climates only slightly warmer than today are sufficient to thaw significant regions of permafrost"- a harrowing conclusion if their conclusions are correct and major regions of permafrost are at risk of defrosting. Indeed already, as the video makes out and as Rachold et al. (2007) concluded there is now evidence that "continuous permafrost is actively thawing in many circum‐Arctic regions".

Despite lots of doom and gloom suggesting studies showing the modelling impacts methane releases from permafrost melting there still remains a vast uncertainty as to what extent, when and if we are to see dangerous methane releases from to be ex permafrost regions in coming decades:

Source: Isaksen et al., 2011

Conclusion on permafrost; easy to sensationalise but hard really to predict; predictions remain wooly despite the potential risks!

In light of length of this discussion here on the risks of methane from defrosting permafrost regions we'll touch on clathrates next week!

Hope to see you back soon!

Methane flaring in Siberia

References:

Vaks, A., Gutareva, O., Breitenbach, S., Avirmed, E., Mason, A., Thomas, A., Osinzev, A., Kononov, A. and Henderson, G. (2013). Speleothems Reveal 500,000-Year History of Siberian Permafrost. Science, 340(6129), pp.183-186.

Isaksen, I., Gauss, M., Myhre, G., Walter Anthony, K. and Ruppel, C. (2011). Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions. Global Biogeochem. Cycles, 25(2), p.n/a-n/a.

Rachold, V., D. Y. Bolshiyanov, M. N. Grigoriev, H.‐W. Hubberten, R. Junker, V. V. Kunitsky, F. Merker, P. Overduin, and W. Schneider (2007), Nearshore Arctic subsea permafrost in transition, Eos Trans. AGU, 88(13), doi:10.1029/2007EO130001. 

O'Connor, F., Boucher, O., Gedney, N., Jones, C., Folberth, G., Coppell, R., Friedlingstein, P., Collins, W., Chappellaz, J., Ridley, J. and Johnson, C. (2010). Possible role of wetlands, permafrost, and methane hydrates in the methane cycle under future climate change: A review. Rev. Geophys., 48(4).

Höglund-Isaksson, L.: Global anthropogenic methane emissions 2005–2030: technical mitigation potentials and costs, Atmos. Chem. Phys., 12, 9079-9096, doi:10.5194/acp-12-9079-2012, 2012.

Looking to the future: Emissions predictions

Happy new year to all from a rather sorry looking, thinly snow covered European Alps!

The low snowfall in the European Alps this winter reminds me of a talk I went to a few weeks ago by James Balog (the man behind the 'Extreme Ice Survey' - http://extremeicesurvey.org for more). 

He has done a really fantastic job of linking science and art through his ongoing study of glaciers in some of the world's most mountainous and polar regions. He poingnently described glaciers as 'the canary in the global coal mine' as he showed clips of glacial retreat the world over. One of his clips was from one of Europe's most significant glaciers the 'Mer de Glace' (The Sea of Ice) about 20 miles away from where I am staying at the moment. I remember visiting this glacier as a young boy, being shocked then to learn about its rapid retreat. As a lover of both photography and of the mountains, spending time exploring the latter whenever I can it was a fantastic talk and I'd recommend his film 'Chasing Ice' which is based on the project to anyone if you haven't already seen it. 

Now back to topic...

This week we look at the complex issue of prediction methane emission into the future and looking at speculative predictions for future anthropogenic methane production as well as the 2 major worries for the future: methane clathrates and the risk of major methane release from defrosting permafrost regions.

Anthropogenic emissions into the future

The period of stabilisation in atmospheric methane levels experienced between 2000 and 2007 sadly appears to be over - growth has been consistent since 2008, passing the 1850ppb mark for the first time in 2014 as the figure below highlights:

Source: NOAA, 2015

Unfortunately predictions for the future aren't optimistic, with Höglund-Isaksson (2012) predicting anthropogenic emissions to break through the 400 Mt/year mark by 2027 and "an expected increase to 414 Mt methane in 2030". The same can be said for natural emissions; "Natural emissions of CH4 are likely to increase in a warmer climate; however, the magnitude and rate of change of future emissions from natural sources are largely unknown." - O'Connor et al (2010).

Source: Höglund-Isaksson, 2012

A sad reality if this is indeed the case, it highlights once again however the growing importance of curbing methane emissions. What though if methane emissions are now out of our control? That anthropogenically stimulated global warming has triggered a tipping point in the arctic in particular and that natural methane emissions from permafrost and methane hydrates are now set to be unleashed? 

References:

Vaks, A., Gutareva, O., Breitenbach, S., Avirmed, E., Mason, A., Thomas, A., Osinzev, A., Kononov, A. and Henderson, G. (2013). Speleothems Reveal 500,000-Year History of Siberian Permafrost. Science, 340(6129), pp.183-186.

Isaksen, I., Gauss, M., Myhre, G., Walter Anthony, K. and Ruppel, C. (2011). Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions. Global Biogeochem. Cycles, 25(2), p.n/a-n/a.

Rachold, V., D. Y. Bolshiyanov, M. N. Grigoriev, H.‐W. Hubberten, R. Junker, V. V. Kunitsky, F. Merker, P. Overduin, and W. Schneider (2007), Nearshore Arctic subsea permafrost in transition, Eos Trans. AGU, 88(13), doi:10.1029/2007EO130001. 

O'Connor, F., Boucher, O., Gedney, N., Jones, C., Folberth, G., Coppell, R., Friedlingstein, P., Collins, W., Chappellaz, J., Ridley, J. and Johnson, C. (2010). Possible role of wetlands, permafrost, and methane hydrates in the methane cycle under future climate change: A review. Rev. Geophys., 48(4).

Höglund-Isaksson, L.: Global anthropogenic methane emissions 2005–2030: technical mitigation potentials and costs, Atmos. Chem. Phys., 12, 9079-9096, doi:10.5194/acp-12-9079-2012, 2012.

The power of cattle

Cattle and methane production

A teaser from Cowspiracy

The film was for a time free to watch on YouTube but has since been removed, it now costs $5 from the website www.cowspiracy.com and I would definitely say its worth paying for and watching. Cowspiracy (IMDB review here) is an independent documentary looking into cattle based agriculture, its dark impacts and why seemingly nobody wants to discuss it.

So... Cowspiracy aside what are the facts and science behind methane production from cattle agriculture? The following video produced by Harper Adams University gives an insight into how methane is produced and to the importance in feed in determining methane production:

Key points: Cows have large fore-stomach containing millions upon millions of bacteria called methanogens. These are good as they enable cows to create energy from foods we are not able to, the downside is that they create the waste product of methane. This study is looking into the role of changing feed types has on methane production - the focus of intense research at present.

So, with 1.5 billion cows in the world today:

Livestock populations of chickens and cattle

Source: The Economist (available here)

... which are thought on average to create approximately 100kg methane each per year it's clear cows alone are a major source of methane and hence driver of climate change.

To get things into perspective!

Data: NASA Goddard Institute for Space Science, Figure: BBC (available here)

What are the options for the future?

• Reducing cow numbers - and the global population adopting a diet less dependent on beef and dairy products
• Making cow production system more efficient - less time between calving and less time spent fattening cows
• Methane entrapment and use as a fuel

Before too long no longer just a joke? 

(Original source unclear) 

• Diet modification - studies such as that being undertaken at Harper Adams university in the video shown above are investigating feeds to determine variations in methane production. Others are adopting a different approach; one American study found after years of trials that natural oregano is able to reduce methane production by 40% when given to cows as a supplement at the appropriate dosage!

So... It appears our love cheese, milk, steaks, beef burgers and so on should probably be calmed if the biggest culprit of anthropogenic methane emissions is to be tamed. Or further perhaps, by adopting vegetarianism as a whole and cutting out all animal products more broadly...

"Nothing will benefit human health and increase chances for survival of life on Earth as much as the evolution to a vegetarian diet" 

(Albert Einstein, Date unknown)

A spotlight on agriculture

It doesn't take much scrutiny of methane emissions data to see the significance of agriculture as the largest component, using Höglund-Isaksson (2012) data for example we see the author has come to a figure of 324Mt CH4 net for anthropogenic sources in 2005. Of this figure 68.7Mt is calculated to come from cattle alone. Pigs were responsible for 5.6Mt and other livestock around the world 22.1Mt. Rice cultivation was responsible for 26.8Mt. This comes to a total of 123Mt before cereals production other than rice is even considered - agriculture is clearly a massive driver of anthropogenic emissions.

The following figure produced with data from the GMI (Global Methane Initiative) portrays the significance of agriculture as a whole to have risen further by 2010 - contributing almost exactly 50% of total anthropogenic methane emissions:

Data: GMI, Figure: SEF (Sustainable Energy Forum), available here

As ruminant animals form over half of agriculture's contribution, of which the majority comes from cattle as highlighted by Höglund-Isaksson cattle will take on the focus of the rest of the next post.

Anthropogenic sources

Anthropogenic emissions

Following up from our post on natural emissions last week this week we turn our attention to the anthropogenic sources. As with natural emissions there is variance just as to the current level of anthropogenic emissions but most figures cite a figure of about 330 Tg/year for 2005 with papers using a more recent reference year being tending to be slightly higher. An extract from the IPCC's AR5 report is shown below:

Anthropogenic methane emissions

Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change

The paper states:

"Anthropogenic CH4 sources are estimated to range between 50% and 65% of the global emissions for the 2000s ... Anthropogenic sources are dominant over natural sources in top-down inversions (~65%) but they are of the same magnitude in bottom-up models and inventories"

This surpassing, or at least equalling in the magnitude of anthropogenic emissions compared to natural emissions is due to the continued growth of emissions in certain sectors in the decades leading up to the turn of the new millennium:

Trends in global emissions of methane (1970-2005)

Source: Emissions Database for Global Atmospheric Research

Significant increases in methane emissions from 'waste' and from 'fugitive emissions from fuel' (which includes the significant component of leaked methane from the production of fossil fuels) were mainly responsible for the continued growth of anthropogenic methane emissions in the last 3 decades of the 20th century. Since 2000 "emissions started increasing again, with an average growth rate of 1.9% per year, which has meant that since 2002, the emissions increased faster than in the last four decades. This led to a global increase of about 20% over the period 2000-2010, driven by increased coal mining by the top methane emitting country China (+50%) and increased cattle numbers in Brazil (+23%)" (IEA, 2012).

The result of these changes since 2000 mean as of 2010 the make-up of anthropogenic emissions is as follows:

Break down of anthropogenic CH4 emissions, 2010

Source: International Energy Agency, available here 

Another interesting way to interrogate anthropogenic sources of methane is geographically - by mapping its emission such as shown here in another graphic by EDGAR (Emissions Database for Global Atmospheric Research):

Mapped anthropogenic methane emissions, 2009

EDGAR, 2009

The blue shading shown in West Bengal and Bangladesh depict the particularly intense 3000-5000 tonnes CH4 emitted per 0.1degree grid cell per year with parts of China being shown to emit 5000 tonnes and above due in part to their intensive coal mining practices and rice agriculture.

So in summary of this week's post we have learnt:

• Anthropogenic methane emissions are at present thought to be approximately 350Tg/year
• This level of emission is at least equal, if not larger than the sum of all natural methane emissions
• Between 2000 and 2010 anthropogenic methane emissions increased by 20%
• Responsible for 43% of methane emissions agriculture is the largest source of anthropogenic methane which we will look into in more detail next week

Any questions or comments please don't hesitate to comment below!

Till next time...

References:

Ciais, P., C. Sabine, G. Bala, L. Bopp, V. Brovkin, J. Canadell, A. Chhabra, R. DeFries, J. Galloway, M. Heimann, C. Jones, C. Le Quéré, R.B. Myneni, S. Piao and P. Thornton, 2013: Carbon and Other Biogeochemical Cycles. In: Cli- mate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 

International Energy Agency, I. (2012). PART III: GREENHOUSE-GAS EMISSIONS. [online] Emissions Database for Global Atmospheric Research. Available at: http://edgar.jrc.ec.europa.eu/docs/IEA_PARTIII.pdf [Accessed 04 Dec. 2015].