Climate controls must cover gases other than CO2

Agriculture is one of the main sources for the greenhouse gas nitrous oxide (N2O) which results from the use of fertilisers. Credit: André Künzelmann/UFZ

Agriculture is one of the main sources for the greenhouse gas nitrous oxide (N2O) which results from the use of fertilisers. Credit: André Künzelmann/UFZ

Cutting emissions of other greenhouse gases would slam the brakes on short-term climate change faster than controlling CO2 alone. But rather than offering an easy way out, warns Jim Butler, director of the Global Monitoring Division at the US National Oceanic and Atmospheric Administration (NOAA), they present both an opportunity and a challenge. “Addressing them can help us see earlier results than we would see with CO2, which poses a problem today but a much bigger one in the future,” he told Simple Climate. “CO2 must be addressed, but ignoring these other gases too could take us to places where we don’t want to go.”

Butler’s division has tracked the levels of different gases in the atmosphere for decades. Among them he says, CO2 rightfully gains most attention. That’s because it traps so much of the sun’s energy, it currently accounts for almost two-thirds of the warming power known as “climate forcing”. “It is responsible for well over 80 per cent of the increase in climate forcing from long-lived gases each year,” Butler said. “It is also very long lived, with around one-fifth of what is emitted hanging around for at least 1,000 years.” Yet as burning oil, natural gas and coal, which produces CO2, propels modern life, cutting the amount we use enough will take some time. “In the meantime there are other gases that could and probably should receive attention,” Butler underlined.

Stephen Montzka of NOAA, along with colleagues Butler and Ed Dlugokencky, looked at exactly how these gases have been affecting climate in top scientific journal Nature this week. Monitoring and evaluating these gases helps show how humans are affecting their levels in the atmosphere. It also serves as a check on the results of claimed emissions. Unfortunately, the amount countries say they produce and levels recorded at observatories across the world disagree. However, Butler noted that no approach is perfect, and that at least comparing the two gave them some idea how far out they were. “The beauty of comparing the two is that each relies on completely different measurements, procedures and assumptions,” he said.

The kindest cuts

The good news is that since 1990, emissions of non-CO2 gases have fallen. That’s thanks to cuts in emissions of chemicals responsible for the hole in the ozone layer  thanks to governments agreeing the Montreal Protocol in 1987. These chemicals are also greenhouse gases that trap energy in the atmosphere.  That reduction more than balanced increases in emissions from CO2 until 2003, showing how big an impact limiting non-CO2 gases can have.

Human greenhouse gas (GHG) emissions, calculated as the difference between total emissions derived from observations and a constant natural background. As a result, any variations in natural fluxes are included in the values presented. The scale on the left is the amount of gases emitted translated into the equivalent amount of CO2 that would produce the same forcing, in units of billions of tonnes per year (Gt CO2 eq yr-1)  Emissions of CO2 from fossil fuel exploitation (ff) and from fossil fuels plus land use change (ff1lu) are from bottom-up inventories provided by governments. CH4 is the chemical formula for methane, N2O is nitrous oxide, ODSs are ozone-depleting substances and HFCs are hydrofluorocarbons. Credit: Nature/NOAA

Human greenhouse gas (GHG) emissions, calculated as the difference between total emissions derived from observations and a constant natural background. As a result, any variations in natural fluxes are included in the values presented. The scale on the left is the amount of gases emitted translated into the equivalent amount of CO2 that would produce the same forcing, in units of billions of tonnes per year (Gt CO2 eq yr-1) Emissions of CO2 from fossil fuel exploitation (ff) and from fossil fuels plus land use change (ff1lu) are from bottom-up inventories provided by governments. CH4 is the chemical formula for methane, N2O is nitrous oxide, ODSs are ozone-depleting substances and HFCs are hydrofluorocarbons. Credit: Nature/NOAA

The remaining greenhouse gases could be harder to control. These include methane, nitrous oxide (N2O), better known as laughing gas, and hydrofluorocarbons. “Methane and N2O both have many sources, mainly biological reactions,” Butler commented. He noted that research was needed to see how best to limit emissions, but some possibilities may be easier than others. “There could be some relatively simple approaches for addressing methane and N2O emissions from the energy and industrial sectors,” Butler said. “Another example would be to begin using nitrogen-containing fertilisers more efficiently to help reduce N2O emissions, but that, too, would need to be done carefully.”

Scientists consider it would be dangerous to exceed a 2°C global average temperature increase, which is why limiting climate change to this amount was a stated aim of the Copenhagen Accord. To prevent this by limiting CO2 alone could require annual emissions in 2050 to be just one-fifth of those in 1990.  But Butler’s figures suggest that cutting all greenhouse gas emissions by that amount would go beyond making forcing, and therefore temperature, stable and instead begin reducing forcing far sooner than focussing only on CO2.

Whether any emissions cuts are made depends ultimately on how committed we, as a society, are to making them, Butler said. “There is no simple solution,” he warned. “One thing is for certain, if society chooses to do little or nothing, these gases will accumulate in the atmosphere, adding yet another blanket to planet Earth, as global population continues to increase and energy demand continues to accelerate.” But because the main other greenhouse gases are broken down in the atmosphere more quickly than CO2, including them in efforts to fight climate change would mean the results would be seen quicker. Paying attention to all such gases would also make a bigger difference than focussing on CO2 alone, Butler explained. “Society has something significant to gain by developing management strategies that include a number of gases,” he said.

The direct radiative forcing (warming effect) of greenhouse gases under various scenarios. a) Red: constant 2008 emissions of both CO2 and non-CO2 greenhouse gases. b) An 80 per cent cut in non-CO2 emissions. c) An 80 per cent cut in CO2 emissions. d) An 80 per cent cut in all greenhouse gas emissions. In all scenarios, emissions cuts are phased in between 2009 and 2050. Credit: NOAA

The direct radiative forcing (warming effect) of greenhouse gases under various scenarios. a) Red: constant 2008 emissions of both CO2 and non-CO2 greenhouse gases. b) An 80 per cent cut in non-CO2 emissions. c) An 80 per cent cut in CO2 emissions. d) An 80 per cent cut in all greenhouse gas emissions. In all scenarios, emissions cuts are phased in between 2009 and 2050. Credit: NOAA

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4 Responses to “Climate controls must cover gases other than CO2”

  1. veronica-mae soar Says:

    Hey — why is such a sensible suggestion not getting headline news ? Why is this not being dumped on the desks of environment ministers around the world ? Even if this chap is only half right it seems to me that taking this notion on board and doing something about it is just common sense (but then, common sense is not so common these days !)

  2. stefanthedenier Says:

    To reduce N2O…? Nitrogen is 78% of the atmosphere – there is plenty of oxygen – any idea how to separate them not to mix?

    I would like to point to you regarding methane (CH4) The most important molecule – to produce as much as possible of it. The truth has being proven; I will keep even this comment as a record, that you have being informed: you will find all the proofs, on my website, page methane + in the PDF form much more: http://globalwarmingdenier.wordpress.com have a nice day

    • andyextance Says:

      Hi Stefan, welcome to Simple Climate. Nitrogen gas is incredibly stable, and doesn’t usually react with oxygen. Much of the nitrous oxide is made by soil and sea bacteria, and nitrogen fertilizer stimulates the soil bacteria to produce even more, which is why Butler made the comment about using fertilizer. It can also be made by human industrial activities, and combustion, as in car engines. As for methane – I’m inclined to go with what the NOAA scientists say, as your site doesn’t say who you are, and why we should listen to you. Thanks for the comment anyway.

      • stefanthedenier Says:

        andyextance, how do you do? I am Stefan, telling the truth. I have read above what Butler said – if you have stomach for the truth; you should compare yourself. His stereotype about methane is bordering on crime. I have proven that the truth is completely the opposite.Read the page on methane on my website, read in the condensed version of the book much more; I can send you a copy of my book. If that Butler had any knowledge about physics and chemistry, he wouldn’t be making such a fool of himself. When the truth is known, everything is on record. Better join the truth, now. Methane is necessary to be produced as much as possible. I


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