Lethal heat waves already before summer: 51,1º C in Pakistan on May 27; 56º C in Iran on June 4; on June 16, 43º C in Portugal, favoring one of the deadliest European forest fires in historical records. On June 19, 49º C in Oklahoma, USA, preventing smaller planes from flying. Extreme temperatures become more extreme, likely, frequent and adverse to plant and animal life at increasing latitudes of the planet as atmospheric concentrations of greenhouse gases (GHG) increase.
After carbon dioxide (CO2), methane (CH4) is the most prominent character in the plot of ongoing anthropogenic climate change. Its importance has been emerging in the last ten years and is expected to grow even more in the next twenty. Research published in December 2016 in Geophysical Research Letters revises upward the impact of anthropogenic methane emissions on the climate system, in relation to the values adopted by the IPCC[1]. According to its authors, considering the period 1750-2011, the radiative forcing of methane (its ability to absorb and retain infrared radiation re-emitted by the Earth in the atmosphere, preventing heat from dispersing into space) “is about 25% higher ( increase from 0,48 W/m2 to 0,61 W/m2) than the value adopted by the 2013 IPCC assessment”[2].
Based on these new calculations, Gunnar Myhre, from Center for International Climate and Environmental Research in Oslo, concludes that “the Anthropogenic methane emissions have already caused a warming effect corresponding to about a third of the effect due to CO2 emissions.”[3]. When it is stated that, in the last decade, methane has definitively entered the picture in the balance of the main causes of climate change, this is the first point to be considered.
The second point concerns the rhythm increase in atmospheric methane concentrations. In 1750, these concentrations were 700 parts per billion (ppb). In 2015, they reached 1.834 ppb, as shown in the figure below.
Between 2000 and 2005, there was a slowdown and such concentrations increased by an average of just 5 parts per billion (ppb) per year. But from 2007 onwards, they started to rise again very quickly. In 2015, they increased by 9,9 ppb, practically double the average rate of increase at the beginning of the century. In the last three years, the curve of atmospheric methane concentrations has been approaching the scenario with the most intense GHG emission, that is, the RCP 8,5 W/m2 scenario proposed by the IPCC, as shown in the figure below[4].
The third point to consider when talking about the increasing contribution of methane to the composition of GHGs in the last decade is the wide range of its emission sources, all of them growing. Before it is burned as natural gas, methane escapes into the atmosphere at all stages of the fossil fuel industry: extraction by hydrofractionation, distribution, storage, consumption, and active and abandoned coal mines. But in addition to emissions linked to fossil energy, even greater quantities of methane are released into the atmosphere by four other main factors:
1. Enteric fermentation of livestock
2. Agriculture and peatland fires
3. Release of methane from hydroelectric plants
4. Thawing of permafrost and methane hydrates
For now, methane emissions are predominantly biogenic, with the fossil industry accounting for 30% to 45% of these emissions and items 1 and 2 (enteric fermentation of livestock, agriculture and peatland fires) accounting for 55% to 70% of them, according to picture below[5].
Another source of methane – hydroelectric plants – is not yet clearly accounted for in calculations of GHG emissions, although it has been quantified, for example, by Philip Fearnside, head researcher at INPA. He shows that “In terms of greenhouse gas emissions, the Balbina dam in Brazil [is] worse than the burning of fossil fuels"[6]. In addition to their brutal socio-environmental impacts, hydroelectric plants are, therefore, large emitters of methane and, contradicting a tenacious commonplace, they do not offer a low-carbon energy matrix.
The fourth factor, certainly the most potentially dangerous, ensuring methane's increasingly central position on the climate scene is the phenomenon of amplification of global warming in the Arctic. According to the World Meteorological Organization report from March 2017, much of the global average warming of 1,1º C above the pre-industrial period reached in 2016 is due to the warming of the Arctic, where average temperatures have already reached, in some areas , at least 3º C above the period 1961-1990 and up to 6,5º C at Svalbard airport, in Norway, a gigantic jump of 1,6º C in relation to the last record. This enormous warming triggers a feedback dynamic, in which the greater heat causes the retreat of sea ice and the melting of terrestrial and marine permafrosts, drastically decreasing the albedo (the fraction of solar radiation re-emitted by the Earth back into space), which increases , in turn, heating and so on.
The most imminent danger of a runaway increase in the release of methane into the atmosphere comes from the East Siberian Continental Sea Shelf (ESAS), as 75% of its 2,5 million km2 area is less than 40 meters deep. Its bed, once covered with ice, is now, given summer temperatures well above freezing, increasingly exposed to solar radiation. It turns out that there are immense amounts of methane, largely in the form of methane hydrates, stored in the sediments of this platform. And as this platform is very shallow, the methane no longer trapped in these hydrates, and also released by bacterial action on the carbon trapped there, is rising in columns of methane bubbles directly into the atmosphere. The rate of acceleration of this process is still the subject of controversy. But it is already underway. “We must remember – and many scientists unfortunately forget – that it is only since 2005 that this summer opening of the ocean has occurred on the Arctic sea shelves. Thus, we are in an entirely new situation, with the occurrence of a new melting phenomenon”, writes Peter Wadhams, in a recent and fundamental book[7].
It is clear that methane remains in the atmosphere for only about 12 years, while CO2 remains on average for one to three centuries (its effect therefore being essentially cumulative).[8]). But the immediate threat of methane is now increasingly greater, as, in terms of global warming potential (GWP), one ton of methane in the atmosphere is equivalent to 72 tons of CO2 over a 20-year horizon.[9].
The next 20 years will indeed be crucial. According to Cambridge scientists, gathered in the Arctic Methane Emergency Group (AMEG), “methane could supplant carbon dioxide and become the largest radiative forcing in the next 20 years”. A AMEG statement states: “the quantities of methane on the marine continental shelf are so vast that the release of just 1% or 2% of this methane could lead to the release of the remaining methane in an unstoppable chain reaction”[10]. And at the press conference at COP20 in Lima, in December 2014, John Nissen, director of AMEG, summarized his conclusions as follows: “the Arctic melting is a catastrophic threat to civilization.”
[1] Cf. M. Etminan, G. Myhre, EJ Highwood, KP Shine, “Radiative forcing of carbon dioxide, methane and nitrous oxide: a significant revision of the methane radiative forcing.” Geophysical Research Letters, 27/XII/2016: DOI:10.1002/2016GL071930. For the values of the radiative forcing of methane and other GHGs, always in relation to the global warming potential (GWP) of CO2, adopted by the IPCC/AR4, based on calculations by G. Myhre, see “Climate Change 2007: Working Group I: The Physical Science Basis”, chap. 2.10.2: Direct Global Warming Potentials:
<http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10-2.html#table-2-14>.
[2]M. Etminan et al. (cit.): “The 1750-2011 [methane] Radiative Forcing is about 25% higher (increasing from 0.48 W m-2 to 0.61 W m-2) compared to the value in the Intergovernmental Panel on Climate Change (IPCC) 2013 assessment”.
[3] See Gunnar Myhre, “Effect of methane on climate change could be 25% greater than we thought”. Cicero, 12/I/2017.
[4]Cf. M. Saunois, RB Jackson, P. Bousquet, B Poulter & JG Canadell, “The growing role of methane in anthropogenic climate change”. Environmental Research Letters, 11, 12, 12/XII/2016: “atmospheric methane concentrations are rising faster than at any time in the past two decades and, since 2014, are now approaching the most greenhouse-gas-intensive scenarios”.
[5]See Adam Vaugham, “Fossil fuel industry's methane emissions far higher than thought”. The Guardian, 5/X/2016; M. Saunois et al. (cit.): “New analysis suggests that the recent rapid rise in global methane concentrations is predominantly biogenic - most likely from agriculture”.
[6] See Philip M. Fearnside, “Why Hydropower is not clean energy”. Scitizen, 9/I/2007; fearnside, “Greenhouse Gas Emissions from a Hydroelectric Reservoir (Brazil's Tucuruí Dam) and the Energy Policy Implications”. Water, Air, and Soil Pollution, January, 2002, 133, 1-4, pp. 69-96: “Tucuruí's emission of greenhouse gases in 1990 is equivalent to 7.0–10.1 × 106 tons of CO2-equivalent carbon, an amount substantially greater than the fossil fuel emission of Brazil's biggest city, São Paulo”
[7] See Peter Wadhams, A Farewell to ice. A report from the Arctic. London, 2016. See also the excellent The death spiral. How humanity altered the climate machine. São Paulo, 2016, by Claudio Ângelo.
[8]This is the average proposed by TJ Blasing, “Recent Greenhouse Gas Concentrations”. CDIAC, April 2016http://cdiac.ornl.gov/pns/current_ghg.html>. Between 65% and 80% of the CO2 released into the atmosphere dissolves in the ocean between 20 and 200 years, but there is a residual “long tail” absorbed over millennia, so that if CO2 emissions were to cease today, their Atmospheric concentrations would only return to pre-industrial levels after more than tens or hundreds of millennia. Cf. D. Archer et al. “Atmospheric Lifetime of Fossil Fuel Carbon Dioxide”. Annu. Rev. Earth Planet. Sci. 2009. 37:117-34http://climatemodels.uchicago.edu/geocarb/archer.2009.ann_rev_tail.pdf>.
[9]Cf. And this only with regard to the direct effects of methane. But it is also necessary to take into account, when calculating its global warming potential, indirect emissions, as methane tends to increase the concentrations of two other greenhouse gases: ozone and water vapor. See the IPCC, chapter cited in note 1.
[10] See if <http://ameg.me/index.php/about-ameg/13-ameg-declaration-of-emergency>.