Now CO2 is short lived, cows really are bad | Brussels Blog

Now CO2 is short lived, cows really are bad

posted by on 20th Oct 2015

Methane or ‘natural gas’ is an important player in UK lifestyles, we heat our homes with it, we generate 30% of our electricity with it and the cattle that provide dairy products and red meat create substantial amounts of it.

The arguments over methane are fraught with controversy. Do leaks of methane make it as climate damaging in creating electricity as coal? Will the leaks from fracking increase the UK’s carbon footprint by much? Should we “kill all the cows and eat them now” to protect the climate?

My experience leads me to believe that the UK Government is not keen to answer such questions (e.g. Buried by Defra?) but there is a debate amongst scientists about what policies should be taken to limit methane emissions – and how soon. Some say we can wait but others see that curbing methane emissions will really help to reduce climate change.

Buying time or loosing time?

Scientists Ramanathan and Victor say that reducing emissions of two powerful and fast-acting causes of global warming – methane and soot – will not stop global warming but it could buy time. This might allow a few decades, for the world to put in place more difficult efforts to regulate carbon dioxide and keep Global Temperature Rise below the so-called danger level of 2°C. However, Ray Pierre Humbert thinks this might detract from the task of reducing the emissions of the main greenhouse gas, carbon dioxide. He says

“Suppose we are outrageously successful, and knock down anthropogenic methane emissions to zero, which would knock back atmospheric methane to a pre-industrial concentration of around 0.8 ppm… This gives us a one-time cooling of 0.4°C.”


“… since methane responds within a decade to emissions reductions, we still get the full climate benefit of reducing methane even if the actions are deferred to 2040.”

This argument relies on:

  • The danger threshold is 2°C and decades away
  • Warming the Earth for a few decades has little effect
  • Carbon dioxide is a long-lived gas

The danger threshold is 2°C and decades away?

James Hansen disagrees. A few months ago, on Australia’s RN breakfast, he said:

“Two degrees is a prescription for disaster that’s actually well understood by the scientific community… This number was chosen because it was convenient. It was thought that will give us a few decades so we can set targets for the middle of the century.”

Warming the Earth for a few decades has little effect?

Professor Peter Cox says “It is of course wrong to suggest that changes in non-CO2 radiative forcing factors do not affect the CO2 emissions cuts required to achieve stabilisation. They do through climate effects on land carbon storage.”

One part of this land carbon storage is the carbon in Arctic permafrost that has recently received attention as in Why This New Study On Arctic Permafrost Is So Scary.

Is carbon dioxide a long-lived gas?

It is said that under ‘ordinary conditions’ carbon dioxide remains in the atmosphere for centuries. As Skeptical Science explains, individual carbon dioxide molecules have a short life time of around 5 years in the atmosphere as they are absorbed by oceans and vegetation but similar molecules are released. The balance between the two gives a time scale for CO2 warming potential out as far as 500 years.

In IPCC AR5 this has changed. Faced with the difficulty of controlling world carbon dioxide emissions a new plan has emerged. This is to extract carbon dioxide from the atmosphere. In No option left but to suck CO2 out of air, says IPCC, Fred Pearce writes

“The new report of the Intergovernmental Panel on Climate Change (IPCC), published on Sunday in Berlin, Germany, says “widespread” use of bioenergy with carbon capture and storage (BECCS) will probably be needed to stop the world warming by 2 °C, the politically agreed danger threshold.”

The IPCC’s report on mitigation assumes the lifetime of CO2 in the atmosphere can be reduced by removing CO2 from the atmosphere – Matching emissions with extractions can reduce the CO2’s atmospheric lifetime to zero. (e.g. Your car emits CO2 into the atmosphere and BECCS takes it out – lifetime zero)

Although Pierre-Humbert said “you can’t ‘unemit’ the CO2 with any known scalable economically feasible technology”, the climate now depends on it.

I believe James Hansen, climate change is already dangerous and the danger threshold is (if there is a threshold) is lower than 2°C. I believe Peter Cox that warming the Earth, even on a temporary basis, has consequences and the excuse “don’t worry about methane emissions because carbon dioxide is much worse” is hollow.

Methane is bad for the climate.

That also means cows are bad for the climate.



Myles Allen on carbon dioxide, methane and soot

Myles Allen has been very influential with the UK Government – I was first directed to his work by Professor David Mackay, then Chief Scientific Adviser of the UK Department of Energy and Climate Change at a conference in 2009. His crucial paper is Warming caused by cumulative carbon emissions towards the trillionth tonne. The gist of this paper is that 1 trillion tonnes of carbon (2.67 trillion tonnes of CO2) can be emitted into the atmosphere before average global temperatures rise by 2°C. (I have argued elsewhere that the climate models used for this paper had serious problems because they omitted important climate feedbacks.)

In The exit strategy (2009), Myles and others said

“Short-term measures that reduce 2020 emissions of potent but short-lived gases but commit to greater emissions of CO2 overall could actually be counterproductive.”

Strictly this is correct. “Reduce methane emissions to go easy on carbon dioxide emissions” is dangerous but it has the worrying implication “Concentrate on carbon dioxide, go easy on methane” – a message that may have been transmitted to UK Government Departments. In a reply to me, David Mackay wrote “[there is the] competing argument from Myles Allen et. al. that methane has too ‘high’ a rating ”.

In Cutting soot and methane distracts from 2C goal, says Oxford scientist, Carbon Brief reported

“Most countries are focusing on reducing CO2 and [methane and soot] at the same time.
But a new policy paper by Myles Allen, professor of geosystem science at the Oxford Martin School at the University of Oxford, says that reducing [methane and soot] while CO2 emissions are still rising could make it more difficult to hit the 2C goal.”

If the control of methane emissions could be deferred because it is short lived and carbon dioxide is very long lived, is this invalidated now that carbon dioxide may become a short lived greenhouse gas?


The key word in your final sentence is “may”. CCS is a “proven technology” but is only used (to my knowledge) where the CO2 captured can be used for enhanced oil recovery. What is missing is a long term secure, documentable storage system of CO2. My preference is to store it in solid chemical form as in limestone. We haven’t woken up to the balance of cost benefit of this ……yet. As for ruminants – not benign, yes we need to have fewer of them. That is accomplished by having fewer people eating less red meat and dairy. Possibly more diffcult than having fewer people traveling less.

Alistair Newbould ( April 2, 2016 at 8:08 am )

On Neven’s arctic Forum I have asked “Does the emphasis on peak temperature sideline other measures?” (1)


I’ve long been worried about the arguments of Ray Pierrehumbert and Myles Allen(2) about short lived climate pollutants [SLCPs]. These seem to imply that SLCPs, such as methane and black carbon, are only important when global temperature is near its peak.

One worry is that the short term rise in global temperatures induces feedbacks – e.g. increased CO2 emissions from stored soil carbon. Another is that since the time of “the peak” is not known with certainty, we won’t know when to start cutting back on SLCPs.

However, I have recently become aware that the short term warming can increase the heat stored in the Earth, e.g. heat in the oceans and in the latent heat of melted ice. (I vaguely remember a comment here some time ago about latent heat and what might happen when the ice is melted from various regions.) I have come across Centuries of thermal sea-level rise due to anthropogenic emissions of short-lived greenhouse gases by Ramanathan et. al.(3)

The “significance” includes:

Our study shows that short-lived GHGs contribute to thermal expansion of the ocean over much longer time scales than their atmospheric lifetimes. Actions taken to reduce emissions of short-lived gases could mitigate centuries of additional future sea-level rise.

Peak temperature arguments appear to say that bad things happen when global temperatures reach a certain threshold but their severity is independent of the path taken too reach that threshold.

This implies that a 2°C increase in global temperatures brings the same problems independent of the heat stored lower in the oceans or how much of the ice caps have melted.

How big is the stored heat and are there consequences other than sea level rise?

Does the emphasis on peak temperature sideline other important measurements?

Should we look for other measurements to supplement global temperature targets?


Geoff Beacon ( March 17, 2017 at 10:48 am )

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