to increased future global warming
Today's global average temperature increase from pre-industrial times is 1.0C which is already having disastrous impacts on all continents.Our global warming commitment in time is practically forever, as it will last over a thousand years. Whatever the eventual warming therefore it is practically irreversible- Susan Solomon PNAS 2009 Irreversible climate change due to carbon dioxide emissions.
The reason for this is the ocean heat lag and mainly the ultra long life time of carbon emissions. It used to be assumed that CO2 lasted in the atmosphere 100-200 years. In the IPCC 2007 assessment 20% of CO2 emissions last 1000 years from an instant CO2 pulse model. How ever a more realisitic model published in 2007 'Long term fate of anthropogenic carbon' found that 'About 75% of CO2 emissions have an average perturbation lifetime of 1800 years and 25% have lifetimes much longer than 5000 years.' Carbon emissions are for sure practically for ever then.
In fact there are two general ways in which we are committed to a far greater degree of warming than we are experiencing today.AS the IPCC 2001 assessment expained in one section on intertia (see top page) There is commitment due to climate system science and unavoidable inertia, and there is commitment because of government policy on climate and energy. The latter is a far greater commitment and should be used for climate change risk assessment. It should be recorded in all assessments as it is most policy relevant. 1. Commitment because of climate, energy and economic policies by governments and the world economy.
Today's global warming commitment due to policy by 2100 is 4.4 C (Climate Interactive).This a total eventual commitment after 2100 of over 8C because of the ocean heat lag.
The world is currently fixed on the worst case high fossil fuel emissions IPCC scenario called A1FI. We have been tracking this worst case scenario since 2002 interrupted only by the global economic recession, caused by the profligate bank mortgage crisis. To some extent we have the opportunity to change this commitment.2. Commitment because of climate system science -unavoidable climate system inertia
The 2008 chart from the International Energy Agency is particularly helpful as it gives an idea of the ocean heat lag commitment as well as impacts at increasing global average temperature increases above pre-industrial.
There are in fact four separate sources of unavoidable warming (that we have published science on) to account for in considering what our actual practical policy relevant unavoidable additional warming is today. They are listed in the chart opposite.
Arctic amplication of global warming is rapidly melting more snow and ice including summer sea ice which is rapidly reducing Arctic albedo cooling. We know the feedback warming from this is large but there is no published science to say how much in temperature increase.
By a simple summation of the warming sources today's unavoidable global warming commitment by 2100 is 3C, and the eventual commitment after 2100 is much higher.All of these committed temperature increases lasting over a thousand years are literal end of the world increases because at 3C (or below) climate change assessments have all crops in all regions declined below today's yields, by an extent than which would be huge decline in world food output.
A person might look at their region of the world today and suppose there is no emergency. There is one highly visible sign and proof of the planetary emergency and that the rapidly changing Arctic. The Arctic changes alone are proof of the planetary emergency. To understand just how dire is the global climate emergency that we are all in, climate change commitment must be understood. Humanity- today's children and all future generations are committed (as in condemned) to a much greater degree of warming than we are experiencing.
Climate science treats commitment to more future warming as limited to the climate system inertia and momentum of the ocean heat lag, and for that the estimates vary widely.
The latest from the 2014 IPCC AR5 assessment.
'The climate system has multiple time scales, ranging from annual to multi-millennial, associated with different thermal and carbon reservoirs. These long time scales induce a commitment warming ‘already in the pipe-line’. At the current (unprecedented) rate of atmospheric CO2 increase the commitment is another 40-70% of the warming at the time of atmospheric stabilization'
(IPCC AR5 WG1 TS TFE 8).
As atmospheric is increasing at a rate (unprecedented) of 15 per year our climate system inertia commitment is 40-70%. The IPCC AR4 estimated 'constant composition' or constant heat at another 0.6C by 2100 from 2000 warming of 0.7C, so another 70% is certainly most likely.
A paper June 2015 paper makes the situation clearer on today's emissions.
' A robust finding of these studies is that the CO2-induced warming persists for many centuries.
[...] Our results indicate that as CO2 continues to accumulate in the atmosphere, the full warming effect of an emission may take several decades, if not centuries to emerge. A large fraction of the warming, however, will be realized relatively quickly (93% of the peak warming is realized 10 years after the emissions for the 1000 PgC pulse). This implies that the warming commitment from past CO2 emissions is (relatively)small, and that future warming will largely be determined by current and future CO2 emissions. Each additional CO2 emission will contribute to warming that will persist almost indefinitely. Thus, emission reductions implemented today will equally benefit current and future generations.'
A 2008 paper is a classic (rare) on combining climate sciecne with ethics, On avoiding dangerous anthropogenic interference with the climate system.. (Ramanathan, Feng) The estimated warming of 2.4°C is the equilibrium warming above preindustrial temperatures that the world will observe even if GHG concentrations are held fixed at their 2005 concentration levels
Climate scientists have 3 definitions of 'commitment'. It is usually applied to the ocean heat lag. A temperature increase at the time of atmospheric GHG stabilization is called the 'realized' or 'transient' warming because it not the the full 'equilibrium' caused by that atmospheric GHG concentration. Because of time lags inherent in the Earth’s climate, warming that occurs in response to a given increase in the concentration of carbon dioxide (“transient climate change”) reflects only about half the eventual total warming (“equilibrium climate change”) NRC Climate Stabilization Targets 2010 p9.There is no one definition of climate change commitment by the scientists. The IPCC AR4 gives thee definitions saying none of them are the actual 'unavoidable' commitment, so here we look at what we call the practically unavoidable commitment - certainly with an all out emergency response. This total real world commitment has not been estimated by the climate science. However in general there are two big sources of commitment.
The largest is our socio-economic lag time to reducing emissions to atmospheric GHG stabilization. Certainly the lack of political will today makes this inertia unlimited, but this cannot be counted in any commitment definition. The IPCC says this is not in its purview to assess in the 2014 AR5 but in the AR5 it refers to a study that makes this committed warming more than 1.0C. This large degree of committed warming is due to the assumption that the expected life time (shelf life) of all power plants(mainly coal) will be allowed to run out before being replaced by clean zero carbon energy sources. This probably why almost all science scenarios for atmospheric CO2 stabilization are 50 years or more. However the IPCC AR4 mitigation charts show we are today committed to a 2.4C warming up to a possible 4C. It is odd that this has received so little attention because the IPCC in 2007 were most definite that action had to be taken NOW.We calculate our future commitment (like all effects of atmospheric GHG pollution by the climate sensitivity- how much will be planet from a unit increase in atmospheric CO2 and other GHGs. According to climate experts James Hansen and also Richard Zeebe the metric we are using is a large underestimate of long term warming because the metric does account for the largest future feedback warming. This immediately greatly increases estimates we have of future commitment.James Hansen has for years warned we are committed to more warming because of GHG warming that is still 'in the pipe'. Today we are 0.8C. There is another 0.8C in the ocean heat lag and Hansen estimates the socio-economic lag to replace all the fossil fuel energy in the world is another 0.8C. This is explained by Hansen by a section he wrote Skeptical Science Why it's urgent we act now on climate change.
- Socio-economic inertia
- Climate system science inertia
James Hansen's famous 2008 350ppm paper is a scientific call for emergency action because we are far above 350 ppm CO2 now practically at 400 ppm. and Hansens words in the paper are If the present overshoot of this
target CO2 is not brief, there is a possibility of seeding irreversible catastrophic effects. Clearly we must be treating climate change as a planetary emergency.One paper that does address commitment is a 2008 paper by Ramanathan and Feng Avoiding Dangerous Climate that calculates the ocean heat lag and the aerosol effect (alone) commits us to 2.4C. This is an important paper because it points that the 'hidden' warming of air pollution aerosol cooling must be included as a commitment today. It is being ignored for policy making. The chart of impacts and temperature increases is modified to show the allowable temperature limit to prevent an impact that is caused by a particular degree of warming - to allow for just the ocean heat lag. Because there are already many disastrous global warming driven impacts happening on all continents we are committed to far worse impacts- even if the world were to respond on an emergency basis. In the case of global warming and climate change the science of climate change commitment must be understood and applied as the most policy relavent guide for policy and planning. In other words we should focus on today's committed warming rathewr than today's global temperature increase. Quite simply the unavoidable climate change commitment means that today's global warming is only a fraction of the unavoidable commitment to future global warming which will result from the heat energy in the climate system caused by the accumulation of heat radiating greenhouse gases in the lower atmosphere today (the radiative forcing).
Sources of total committed warming
o Socio-political lag
o Time taken to stabilize atmospheric GHGs
o Ocean heat lag
Ultra-long atmospheric life time of CO2
o Unmasking of air pollution aerosol cooling (Mar 2016 30% of warming masked)
o Carbon feedback amplifying responses to global warming
Committed warming is a term used in the first 1990 expert report on a limit to global warming. (1990 Stockholm Environment Institute Targets and Indicators of Climatic Change F. Rijsberman, R. Stewart) 'Two absolute temperature targets for committed warming were identified. They were 1C and 2C.
International Energy Agency impacts 2008
CLIMATE SYSTEM EMERGENCY INSTITUTE
The health and human rights approach to climate change
Oct 2016 C. Snydrer Evolution global temp past 2M yrs. Earth system sensitivity of 9C ...today’s greenhouse gas levels may already commit Earth to an eventual total warming of 5 degrees Celsius over the next few millennia
March 2015 K. Zickfeld
The time lag between a carbon dioxide emission and maximum
warming increases with the size of the emission
Dec 2014 K. Caldiera
Maximum warming occurs about one decade after a carbon dioxide emission
Sept 2014 S. Leahy We Have Five Years to Stop Building Coal Plants and Gas-Powered Cars
2008 Ramanathan, Feng On avoiding dangerous anthropogenic interference with the climate system..
2001 R, Wetherald. Committed warming and its implication to climate change
The 2014 IPCC assessment estimates the commitment due to atmospheric greenhouse gases at 2.0C.
The commitment from constant greenhouse gas concentrations would correspond to approximately 2C warming IPCC AR5 WG1 12.5.2.
This IPCC commitment does not include the extra warming from amplifying feedbacks in any of its projections.
'However, this equilibrium estimate is based on feedbacks estimated for the present day climate. Climate and carbon cycle feedbacks may increase substantially on long time scales and for high cumulative CO2 emissions' (IPCC AR5 WG1 Ch.12 p.1109)
The first 1990 IPCCC assessment estimated that we are locked in to double today's warming, and the 2011 NRC Climate Stabilization Targets has the same estimate. That makes today's (2016) warming a commitment to 2C.
The IPCC AR5 estimates that commitment is at least an extra 0.6C by 2100 and over another 1C by 2300. That is over 2C (2016).
'AOGCMs estimated a most likely value of about 0.6°C for 2100 (relative to 1980–1999, AR4). CMIP5 results are consistent with those numbers, with an additional warming of about 0.5°C 200 years after stabilization of the forcing'. (AR5 WG1 CH12 p 1103). This does not include amplifying feedbacks.
Certainly then if we include amplifying feedbacks committed warming to equilibrium will be more than double today's warming.
Fossil carbon has taken millions of years to form by burial of living organisms pressure and heat.
Coal, oil, gas and limestone are the forms of fossil carbon.