Plan A might fail … so we need Plan B

23rd May, 2010 - Posted by admin - Comments Off

The need for (another) Plan B for Climate Change Mitigation
Summary
Plan A is the UK Government’s current plan for addressing climate change. It relies on reducing the emissions of long lived greenhouse gases, especially, during this century (especially carbon dioxide) with an emphasis on keeping their level in the atmosphere below an all important peak level at which dangerous climate change becomes probable.
A view amongst some respected scientists is that Plan A does not sufficiently cater for the risk of triggering dangerous climate change in the next few decades. Plan B is designed to further reduce the risk of dangerous climate change by limiting global temperature rises over this shorter time span.
Plan B places more emphasis on the reduction of short term climate forcing agents such as methane and black carbon. It advocates geoengineering schemes to reduce the amount of sunlight reaching the Earth’s surface and employs methods for extracting carbon dioxide from the atmosphere. Plan B may initially divert some of the effort put into reducing the emissions of long-lived greenhouse gases.
Climate feedbacks
Notes from a conversation (12th November 2009) with Professor Peter Cox quote him as saying:
There should be a plan B for climate change if reducing emissions of CO2 cannot be effected soon enough. This would take more seriously the effects of pathways with shorter timescales than CO2, such as methane, ozone (NOx as a precursor) and black carbon. Plan B should also consider geoengineering: Sulphate [released into the upper atmosphere] looks best.
There is another reason for a Plan B – unexpected climate feedbacks that are underestimated or not acknowledged by Plan A. Feedbacks occur when increasing temperature (or greenhouse gas concentrations) trigger mechanisms, which further contribute to global warming.  An example of a feedback is the release of methane from the Arctic tundra and Arctic seas. This is great interest because methane is a powerful greenhouse gas and there are very large quantities stored in the Arctic. There have been recent reports of increased methane emissions in the Arctic. See Science, “Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf” by Shakhova et.al.  (http://www.sciencemag.org/cgi/content/short/327/5970/1246)
Another feedback is happens when melting ice cover in the Arctic leaves area of open sea. Professor Wadhams Professor Peter Wadhams, from the University of Cambridge. Professor Wadhams has been studying the Arctic ice since the 1960s.
The case of Arctic ice is somewhat of a tipping point since the open water created during summer warms up, to about 5C at present, and this
slows down the subsequent autumn freeze up, giving less winter growth. The area of multi-year ice is also shrinking to the point where almost the whole ice cover will be susceptible to summer melt. It may grow back a little in a cold winter but in my view it can never get back to its original situation of, say, 40 years ago. In this sense it has passed through a tipping point.
A Plan B is needed because the UK Government’s current plan, Plan A, does not cope with these contingencies:
A failure to control global greenhouse emissions in the coming decades
Feedbacks reacting more strongly than expected to global warming.
The UK Government’s Plan
Government thinking is that the total amount of carbon dioxide emitted is important – not precisely when the emission occurs. This work clearly is influenced by the work of Allen et al, “Warming caused by cumulative carbon emissions towards the trillionth tonne”. They say
“Total anthropogenic emissions of one trillion tonnes of carbon (3.67 trillion tonnes of CO2), about half of which has already been emitted since industrialization began, results in a most likely peak carbon-dioxide induced warming of 2 degrees Celsius above pre-industrial temperatures, with a 5–95% confidence interval of 1.3–3.9 degrees Celsius”
It is apparent that certain climate feedbacks have not been incorporated into some of the computer simulations used by Allen et. al.
The peak level of carbon dioxide is the keystone in current government thinking. It is the basis for the current “Plan A”, which aims to limit global warming to 2 degrees Celsius.
The Committee on Climate Change
In “Building a low-carbon economy” (December 2008), the Committee on Climate Change say:
“The UK should strongly support a global commitment to cutting GHG emissions by at least 50% below current levels by 2050, with total global Kyoto GHG emissions between 20-24 billion tonnes CO2e in 2050, and with further reductions to between 8-10 billion tonnes CO2e required by 2100. Cuts of this scale would limit our central expectation of temperature rise by 2100 to as close to 2°C as possible, and reduce the risk of extremely dangerous climate change to very low levels (e.g. less than a 1% chance of 4°C temperature rise). CO2e concentrations would peak at around 500ppm by the end of the century before falling towards 450ppm.”
The emphasis on long-lived greenhouse gases is consistent with Plan A. The attitude to short-lived species, such as methane,  can be summarized as
“By the time peak temperature occurs any methane released now will have been removed from the atmosphere by natural processes so it will not affect global warming at the all-important peak.”
Plan A and Plan B compared
Plan A aims at keeping levels of long-lived greenhouse gases below an “safe” maximum level in order to limit the rise in global temperatures to below 2 degrees Celsius – regarded as a limit beyond which dangerous climate change can occur.  It is a long-term plan, the maximum concentration occurring about 2050.
Plan B aims at limiting temperature rises over a shorter time span – starting now. It places more emphasis on the reduction of short term climate forcing agents to limit temperature rises, and reduce the risk of feedbacks, in the next decade or so. This may temporally divert effort from reducing the emissions of long-lived greenhouse gases.
Plan A runs the risk of (a) triggering mechanisms that produce unexpectedly large positive climate feedbacks as temperature rises and (b) larger than expected global greenhouse gas emissions from other nations, leading to a breach the safe maximum limits of greenhouse gases. Plan B contains these dangers by cutting global warming in the near term but it may place a larger burden on future generations to deal with long-lived greenhouse gases.
Plan A assumes that the mechanisms driving climate change are well known – both in type and magnitude – and plans appropriate emission reductions. It also assumes that the necessary reductions in global emissions of greenhouse gases can be achieved. Plan B assumes that the nature of climate mechanisms are not known well enough and neither is the outcome of international negotiations to limit greenhouse gases. It demands an immediate effort to reduce the rise in global temperatures.
Plan B has the advantage of flexibility – by concentrating on short-term temperature reduction Plan B would buy time for dealing with long-term greenhouse gases. The prize in the case of Plan B would be to avoid climate feedbacks that are unexpected (or unexpectedly large) leading to irreversible climate change in a shorter timespan than envisaged by Plan A.
Plan B and long-term greenhouse gases
In a timescale – probably only slightly longer than that in Plan A – it will be necessary to limit the atmospheric concentrations of long-term greenhouse gases as eventually these alone could force the climate above a danger threshold.
Plan A aims to keep below the danger threshold mainly by reducing carbon dioxide emissions. But there are other possibilities of reducing the concentration of carbon dioxide in the atmosphere, such as actually extracting it from the atmosphere and sequestering it. These options are available within Plan B. Examples of activities that extract carbon dioxide from the atmosphere are
Constructing buildings from wood from sustainable sources
Generating power from biomass with associated carbon capture and storage
Using biochar to capture carbon and enhance agricultural productivity.
At the International Conference on Biochar in 2008, Joannes Lehman, the world’s leading proponent the use of biochar, stated that:
“To fully understand the potential of biochar, we have to realise that there’s a large amount of carbon dioxide cycling annually from the atmosphere into the biomass by photosynthesis, being recycled by micro organisms, back to the atmosphere.  This is a huge amount of carbon that is cycling annually between the atmosphere, the plants and back to the atmosphere. So much that every few years (actually about fourteen years), the entire atmosphere has gone once through the biomass, (the plant biomass) and back out again.
If we capture only a small proportion of that carbon annually fixed by photosynthesis and are able to divert it from this fast biological carbon cycle into a much slower cycling, biochar cycle, we have a technology that then delivers net reductions of CO2 in the atmosphere.
If you compare this annual cycle, that’s about sixty or eighty gigatonnes of carbon through the plant biomass, with the annual anthropogenic emissions that are anywhere in the neighbourhood of seven or nine gigatonnes annually then you realise that we only need a small fraction of this annually cycling carbon to be captured into a biochar cycle to put a significant dent into the emissions.”
In addition, Plan B would consider geoengineering projects, such as releasing sulphate into the upper atmosphere to partially shield the Earth from the Sun’s radiation.  This mimics the natural process which occurs following volcanic explosions and eruptions.
Practical differences between Plan A and Plan B
Policy differences between Plan A and Plan B can be seen from considering Unger et. al. “Attribution of climate forcing to economic sectors”. This paper aggregates climate forcing agents and attributes them to broad economic sectors. “Industry”  is one of these economic sectors.
Unger et. al. estimate  the effect of “Industry” on climate over the period of a century: It is assumed that the emissions continue at a constant rate for the whole century. At the beginning of the century “Industry” has a net cooling effect through the emissions of  sulphate and aerosols. But these are short-lived. After about forty years the effects of longer lived species – nitrous oxide and carbon dioxide – accumulate to balance this cooling. After a century has passed the effect of a century of emissions is strongly warming.
If “Industry” were stopped at the beginning of the century, there would be an initial  warming effect followed by a stronger cooling effect later in the century. Stopping such a major section of economic activity is too unrealistic to even be a thought experiment – but, if it were to happen, the initial warming effect of “stopping Industry” could  push the climate past the the dangerous 2 degrees Celsius limit. More practical examples are not hard to find. Consider the use of  internal combustion engines. Are they best  fueled by  petrol (gasoline) or diesel?
The entry in Wikipedia on diesel has
Diesel-powered cars generally have a better fuel economy than equivalent gasoline engines and produce less greenhouse gas emission.
and
Diesel combustion exhaust is a major source of atmospheric soot [black carbon] and fine particles, which is a fraction of air pollution implicated in human heart and lung damage.
Plan A would favour the use of diesel over petrol because of it produces less long term climate warming. Plan B would favour petrol over diesel because it avoids the short term warming caused by soot in diesel exhaust.
Plan B will give further options if, in the short term:
1.unexpected positive climate feedbacks occur
2.there is a serious failure to meet emission reduction targets
Plan B’s further options would include a more drastic reduction in the emissions of long-lived greenhouse gases or the extraction of carbon dioxide from the atmosphere.
Plan A leaves no options available if these contingencies occur.
Summary
Plan A is government’s current model for addressing climate change. It relies on mitigating the emissions of long lived greenhouse gases, especially carbon dioxide, during this century with an emphasis on keeping the level below an all important peak level. Plan B would take the role of shorter lived greenhouse forcing agents more urgently and consider geoengineering and ways to extracting carbon dioxide from the atmosphere.
Postscript : Climate Impacts of Black Carbon
V. Ramanathan from the Scripps Institution of Oceanography recently gave a testimonial to the House Select Committee on Energy Independence and Global Warming. It contained
At current rate of emission (35 billion tons per year) and the current growth rate of 2% to 3%, the manmade greenhouse effect can double during this century. BC reductions [Black Carbon reductions], even at 50%, cannot offset the CO2 effect. However, BC reductions when combined with reductions in other short lived climate warming gases, can delay large warming by few decades and complement CO2  mitigation efforts.
http://globalwarming.house.gov/files/HRG/031610BlackCarbon/ramanathan_part1.pdf
House Hearing entitled: Clearing the Smoke: Understanding the Impacts of Black Carbon Pollution, March 16, 2010

The need for a Plan B for Climate Change

Summary

Plan A is the UK Government’s current plan for addressing climate change. It relies on reducing the emissions of long lived greenhouse gases, especially carbon dioxide, during this century. It emphasises keeping the level long lived greenhouse gasses below a peak level at which dangerous climate change becomes probable.

The view of some respected scientists is that Plan A does not address the risk of triggering dangerous climate change sooner than expected. Plan B is delays global temperature rises by means that have an immediate effect. It places emphasis on the reduction of short term climate forcing agents such as methane and black carbon. It also advocates geoengineering schemes to

  • reduce the amount of sunlight reaching the Earth’s surface
  • extract carbon dioxide from the atmosphere.

Plan B and climate feedbacks

Professor Peter Cox, a leading climate scientist, says:

There should be a plan B for climate change if reducing emissions of CO2 cannot be effected soon enough. This would take more seriously the effects of pathways with shorter timescales than CO2, such as methane, ozone (NOx as a precursor) and black carbon. Plan B should also consider geoengineering: Sulphate [released into the upper atmosphere] looks best.

There is another reason for a Plan B - underestimated  or unacknowledged  climate feedbacks. Feedbacks occur when increasing temperature trigger mechanisms, which further contribute to global warming.  One example is the release of methane from the Arctic tundra and Arctic seas. This is important because methane is a powerful greenhouse gas and there are very large quantities stored in the Arctic. There have been recent reports of increased methane emissions in the Arctic. See Science, “Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf” by Shakhova et.al.  (http://www.sciencemag.org/cgi/content/short/327/5970/1246)

Another feedback happens when melting Arctic sea ice  leaves areas of open sea. Professor Peter Wadhams, who has been studying the Arctic ice since the 1960s says:

The case of Arctic ice is somewhat of a tipping point since the open water created during summer warms up, to about 5C at present, and this slows down the subsequent autumn freeze up, giving less winter growth. The area of multi-year ice is also shrinking to the point where almost the whole ice cover will be susceptible to summer melt. It may grow back a little in a cold winter but in my view it can never get back to its original situation of, say, 40 years ago.  In this sense it has passed through a tipping point.

Plan B is needed because the UK Government’s current plan, Plan A, does not cope with these contingencies:

  • A failure to control global greenhouse emissions soon
  • Feedbacks reacting more strongly than expected.

The UK Government’s Plan

Government thinking is that the total amount of carbon dioxide emitted is important – not precisely when the emissions occur. This view is clearly influenced by Allen et al, “Warming caused by cumulative carbon emissions towards the trillionth tonne”. They say

Total anthropogenic emissions of one trillion tonnes of carbon (3.67 trillion tonnes of CO2), about half of which has already been emitted since industrialization began, results in a most likely peak carbon-dioxide induced warming of 2 degrees Celsius above pre-industrial temperatures, with a 5–95% confidence interval of 1.3–3.9 degrees Celsius.

http://www.nature.com/nature/journal/v458/n7242/full/nature08019.html

It is apparent that certain climate feedbacks have not been incorporated into the computer simulations used by Allen et. al. but this paper has installed the peak level of carbon dioxide as the keystone in current government thinking.

The Committee on Climate Change

In “Building a low-carbon economy” (December 2008), the Committee on Climate Change say:

The UK should strongly support a global commitment to cutting GHG emissions by at least 50% below current levels by 2050, with total global Kyoto GHG emissions between 20-24 billion tonnes CO2e in 2050, and with further reductions to between 8-10 billion tonnes CO2e required by 2100. Cuts of this scale would limit our central expectation of temperature rise by 2100 to as close to 2°C as possible, and reduce the risk of extremely dangerous climate change to very low levels (e.g. less than a 1% chance of 4°C temperature rise). CO2e concentrations would peak at around 500ppm by the end of the century before falling towards 450ppm.

This emphasis on long-lived greenhouse gases is consistent with Allen et. al. The attitude to short-lived species, such as methane,  can be summarized as

By the time peak temperature occurs any methane (or other short-lived species) released now will have been removed from the atmosphere by natural processes so will not affect global warming at the all-important peak.

Plan A and Plan B compared

Plan A aims at keeping levels of long-lived greenhouse gases below an “safe” maximum level in order to limit the rise in global temperatures to below 2 degrees Celsius – regarded as a limit beyond which dangerous climate change can occur.  It is a long-term plan, the maximum concentration occurring towards the end of the century. Plan B limits temperature rises over a shorter time span. It places more emphasis on the reduction of short lived climate forcing agents (e.g. methane and soot) to reduce the risk of feedbacks. It also extracts carbon dioxide from the atmosphere.

Plan A runs the risk of

  • triggering unexpected climate feedbacks as temperature rises
  • larger than expected global greenhouse gas emissions

Plan B delays global warming, allowing more time to cut the emissions of long-lived greenhouse gases and engineer them from the atmosphere. V. Ramanathan from the Scripps Institution of Oceanography recently gave a testimonial to the House Select Committee on Energy Independence and Global Warming. His testimonial gives support to this idea:

At current rate of emission (35 billion tons per year) and the current growth rate of 2% to 3%, the manmade greenhouse effect can double during this century. BC reductions [Black Carbon reductions], even at 50%, cannot offset the CO2 effect. However, BC reductions when combined with reductions in other short lived climate warming gases, can delay large warming by few decades and complement CO2  mitigation efforts.

http://globalwarming.house.gov/files/HRG/031610BlackCarbon/ramanathan_part1.pdf

Plan B also extracts carbon dioxide from the atmosphere so does not rely solely on cutting emissions.  We need Plan B because Plan A may be already failing.

Posted on: May 23, 2010

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