Category Archives: greenhouse gases

Three women meteorologists for International Women’s Day 2017

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On International Women’s Day 2017 I could write about famous women that lots of people (although still not enough) already know about. I could write honouring the wonderful women in my life, but other social media platforms are the way to do that. Instead I would like to introduce you to three influential voices of women in Meteorology, recognising my multiple work roles as a climate scientist, President of the Royal Meteorological Society and Dean for Diversity and Inclusion. Forgive the length of the post, there is so much to say about each!

Eunice Foote (1819-1888) was both a scientist and a proponent of women’s rights. As has come to light over only the past few years (work by Sorenson in 2011, and more recently Katherine Hayhoe), Foote conducted early work on what we now call the greenhouse effect. The experiments investigated the warming effect of the sun on air, including how this was increased by carbonic acid gas (carbon dioxide), and bear a striking resemblance to some outreach experiments still used today. She also speculated on how an atmosphere of this gas might affect climate. “An atmosphere of that gas would give to our earth a high temperature; and if as some suppose, at one period of its history the air had mixed with it a larger proportion than at present, an increased temperature from its own action as well as from increased weight must have necessarily resulted.”

Her paper “Circumstances affecting the heat of the sun’s rays,” was presented by Prof. Joseph Henry at the American Association for the Advancement of Science meeting in 1856, three years before Irish scientist John Tyndall started working on the gas. Interestingly, a contemporary account describes the occasion as follows: “Prof. Henry then read a paper by Mrs. Eunice Foote, prefacing it with a few words, to the effect that science was of no country and of no sex. The sphere of woman embraces not only the beautiful and the useful, but the true.”

Eunice was a member of the editorial committee for the 1848 Seneca Falls Convention, the first women’s rights convention to be organized by women, and one of the  68 women and 32 men who signed the convention’s Declaration of Sentiments.  One of the opening paragraphs of this declaration, based on the Declaration of independence reads:

“We hold these truths to be self-evident: that all men and women are created equal; that they are endowed by their Creator with certain inalienable rights; that among these are life, liberty, and the pursuit of happiness; that to secure these rights governments are instituted, deriving their powers from the consent of the governed. Whenever any form of government becomes destructive of these rights, it is the right of those who suffer from it to refuse allegiance to it, and to insist upon the institution of a new government, laying its foundation on such principles, and organizing its powers in such form, as to them shall seem most likely to effect their safety and happiness”

And it concludes:

“In entering upon the great work before us, we anticipate no small amount of misconception, misrepresentation, and ridicule; but we shall use every instrumentality within our power to effect our object.”

This strikes me as still relevant to both Equality and climate change work today.

Eleanor Ormerod (1828-1901) was the first woman to be made a Fellow of the Royal Meteorological Society. Passionate about insects from childhood, she became an authority on “Injurious insects and Farm Pests”. Her works was honoured in time by Royal Horticultural Society who awarded her the Flora medal, the Royal Agricultural Society who appointed her as consulting entomologist, the University of Moscow from whom she received silver and gold medals from the University of Moscow for her models of insects injurious to plants and the Société nationale d’acclimatation de France who awarded her a silver medal.

Eleanor often tested out the effect of insects on herself, for example:

“Miss Ormerod, to personally test the effect, pressed part of the back and tail of a live Crested Newt between the teeth.”The first effect was a bitter astringent feeling in the mouth, with irritation of the upper part of the throat, numbing of the teeth more immediately holding the animal, and in about a minute from the first touch of the newt a strong flow of saliva. This was accompanied by much foam and violent spasmodic action, approaching convulsions, but entirely confined to the mouth itself. The experiment was immediately followed by headache lasting for some hours, general discomfort of the system, and half an hour after by slight shivering fits.” –Gadow, 1909

Eleanor’s link with meteorology came via her brother, much of her interest being in the relationship of weather to insects. She compiled and analyzed weather data extensively, and published in the Quarterly Journal of the Royal Meteorological Society. I chose Eleanor because of the link between entomology, my late father’s field, and meteorology, mine. In addition, she is said to have been the inspiration for Gaskells heroine in Wives and Daughters and for a short story by Virginia Woolf; an excellent cross-over between science and literature.

(Gadow, Hans 1909. Amphibia and Reptiles. Macmillan and Co. London.)

Joanne Simpson (1923-2010) was the first female meteorologist with a Ph.D. Fascinated by clouds as a child, she might well have gone into astrophysics were it not for the intervention of World War II. As a trainee pilot she had to study meteorology and after getting her training from Carl Gustaf Rossby’s new World War II meteorology programme, spent the war years teaching meteorology to Aviation cadets. Her PhD work focussed on clouds, then regarded as not a particularly important part of the subject, but her early research based revealed cloud patterns from maps drawn from films taken on tropical flights. Subsequently she went on to show how tropical “hot tower” clouds actually drive the tropical circulation, and to propose a new process by which hurricanes maintain their “warm core”.

Following stints at UCLA, NOAA and the University of Virginia, Joanne ended up at NASA Goddard Space Flight Centre where for the first time she met other women meteorologists. It was here that she made what she described as the single biggest accomplishment in her career. She was asked to lead the “study” science team for the Tropical Rainfall Measuring Mission (TRMM) – a satellite carrying the first space-based rain radar. Working with project engineers and recruiting many scientists, Joanne worked on TRMM from 1986 until its launch in 1997. TRMM has led to many discoveries about tropical rainfall, including in 2002 the ability to estimate latent heat in the tropics. This work linked directly back to Joanne’s early work on tropical cloud processes.

Rightly recognised, Joanne was granted membership to the National Academy of Engineering, awarded the Carl-Gustaf Rossby Award (the highest honor bestowed by the American Meteorological Society), presented with a Guggenheim Fellowship. I chose Joanne because she served as President of the American Meteorological Society, as I am serving as President of the Royal Meteorological Society this year. You can read much more about Joanne Simpson in this excellent portrait at NASA.

A significant revision to the climate impact of increasing concentrations of methane

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Summary and Frequently Asked Questions relating to the paper:

Radiative forcing of carbon dioxide, methane and nitrous oxide: A significant revision of the methane radiative forcing by M. Etminan, G. Myhre, E.J. Highwood and K.P.Shine., Geophys. Res. Lett, 43, doi:10.1002/2016GL071930

Just when I thought it was safe to take a holiday, our paper presenting new detailed calculations of the radiative forcing for carbon dioxide, nitrous oxide and methane was published in Geophysical Research Letters on 27th December. For me, this paper was a blast from the past, as one of the first papers I wrote as a postdoc in 1998 was on a similar topic,  and shares 3 out of 4 authors, myself, Keith Shine and Gunnar Myhre.

The recent paper, co-authored with PhD student Maryam Etminan, describes new research on methane’s climate impact that has been performed at the Department of Meteorology at the University of Reading, UK and the Center for International Climate and Environmental Research – Oslo (CICERO) in Norway; it indicates that the climate effect of changes in methane concentrations due to human activity has been significantly underestimated. It also uses these detailed calculations to revise the simplified expressions for estimating radiative forcing adopted by the Intergovernmental Panel on Climate Change (IPCC). The new calculations indicate that the direct effect of increases in the concentration of methane on climate is 25% higher than represented by the expressions previously adopted by the  IPCC, making its present-day radiative forcing (relative to pre-industrial values) about one-third as powerful as carbon dioxide.

The paper has attracted some attention on social media as the calculations may have an impact on policy decisions in the future. Therefore I take the opportunity here, with much of the text below written by my co-author Keith Shine, to both summarise the study and answer some of the questions that have arisen so far.

Does this mean that our previous estimates of radiative forcing due to carbon dioxide have been over-estimated?

No. Carbon dioxide remains the most significant greenhouse gas driving human induced climate change.

In fact in this study we also looked at the estimates of forcing due to carbon dioxide using the same physical understanding as used for methane, and found forcing very similar to previous estimates, except for some underestimation at very high carbon dioxide concentrations.

So if the forcing due to methane has been underestimated in the past, why hasn’t the global mean temperature increased more?

The climate impact (e.g. temperature change) resulting from a radiative forcing change in the atmosphere depends on both the radiative forcing and how the climate system responds to that forcing. Although we have shown that the carbon dioxide forcings are little different to our earlier calculations, there are other changes that cause a radiative forcing that have documented very large uncertainties, for example aerosols (and in particular their impact on clouds) that could easily counteract the additional forcing from methane. Even if we knew the forcing accurately, the uncertainty in the climate response is also large enough that it isn’t a problem to reconcile the observed temperature changes. We are in fact refining the uncertainties through this type of study.

So why the focus on methane?

Human activity has led to more than a doubling of the atmospheric concentration of methane since the 18th century. Methane is a powerful greenhouse gas. It is the second most important greenhouse gas driving human-induced climate change, after carbon dioxide. Its warming effect had been calculated to be about one-quarter of that due to carbon dioxide. Methane emissions due to human activity come from agricultural sources, such as livestock, soil management and rice production, and from the production and use of coal, oil and natural gas.

What did you do that was different?

Previous calculations had focused attention on the role of methane in the “greenhouse” trapping of infrared energy emitted by the Earth and its atmosphere, primarily at wavelengths of around 7.5 microns. The vital element in the new research is that detailed account is taken of the way methane absorbs infrared energy emitted by the Sun, at wavelengths between 1 and 4 microns.

The effect of this additional absorption of Sun’s infrared radiation is complicated, as it depends on the altitudes at which the additional energy is absorbed. This determines whether the extra absorption enhances or opposes the greenhouse trapping. It has been known for many years that the absorption of the Sun’s energy by carbon dioxide reduces its climate effect by about 4%, because much of the additional absorption happens high in the atmosphere.

The new calculations of the effect of methane indicate that much of the extra absorption is in the lower part of the atmosphere, where it has a warming effect. The research shows that clouds play a particularly important role in causing this enhanced warming effect. Clouds scatter some of the sun’s rays back into space; it is the additional absorption of these scattered rays by methane that drives the warming effect, a factor that had not been included in earlier studies.

Are these results important for climate change negotiations?

The new calculations are important for not only quantifying methane’s contribution to human-induced climate change, but also for the operation of the Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC). This takes into account emissions of many greenhouse gases in addition to carbon dioxide. The emissions of these other greenhouse gases are given a “carbon-dioxide equivalence” by multiplying them by a quantity called the “100-year Global Warming Potential” GWP(100); a similar approach is likely to be adopted by most countries for the operation of the UNFCCC’s more recent Paris Agreement.

The GWP(100) for methane includes not only its direct impact on the Earth’s energy budget, but methane’s indirect role, via chemical reactions, on the abundance of other atmospheric gases, such as ozone. Applying the results of the new calculations to the value of the GWP(100) presented in the Intergovernmental Panel on Climate Change’s (IPCC) most recent (2013) assessment, enhances it by about 15%. This means that a 1-tonne emission of methane would be valued the same as 32 tonnes of carbon dioxide emissions, up from the IPCC’s most recent value of 28. Hence for countries with large emissions of methane due to human activity, it would lead to a significant re-valuing of their climate effect, relative to emissions of carbon dioxide.

Can you be more specific about that?

In fact the GWP values have changed substantially due to new research since the Kyoto Protocol, and these changes are reported in the IPCC reports.

CO2 remains the dominant greenhouse gas emission from both developed (so-called Annex1) countries (77%) and non-Annex1 (65%) countries but using our revised value in place of the IPCC AR5 value, methane emissions now exceed 40% of CO2 emissions in developing countries, in CO2 equivalent terms, up from 36%. In developed countries, they are now almost one-quarter of the CO2 emissions (23% up from 20%).

 

So when might these new values influence policy?

The research team identified a number of uncertainties in the calculation of this enhanced absorption by methane, which will require further research to reduce. The new results are unlikely to be recommended for adoption in international treaties until they have been fully considered by the assessment process of the Intergovernmental Panel on Climate Change.

The new research was partly funded by the Research Council of Norway, and the UK’s Natural Environment Research Council.

The full paper is   Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing by M. Etminan, G. Myhre, E. J. Highwood, and K. P. Shine, Geophysical Research Letters, published online 27 December 2016, DOI: 10.1002/2016GL071930

It is open access and can be found at http://onlinelibrary.wiley.com/doi/10.1002/2016GL071930/full

 The IPCC working group 1 (2013) assessment report “Climate Change 2013, The Physical Science Basis can be found at https://ipcc.ch/report/ar5/wg1/