“The rise of atmospheric CO2 above 450 parts per million can be prevented only by an unprecedented (in both severity and duration) depression of the global economy, or by voluntarily adopted and strictly observed limits on absolute energy use. The first is highly probable; the second would be a sapient action, but apparently not for this species.” – Vaclav Smil, Correspondence, Nature, Vol 453, 8 May 2008.
“We can see from the past what we face in a future we have created. The geological record holds a rich history for scrutiny.” Peter D. Ward, The Flooded Earth, 2010.
It turns out that it is possible to forecast our climate future with some degree of accuracy because we know what happened on Earth in the past. Past climates are at least a first order approximation to future climates. We do not know how much fossil fuel we have left and we do not know what the human response to entropy problems will be but if we know how much we will use we can calculate the resultant increase in atmospheric carbon dioxide and compare that to past climates.
To my knowledge all credible estimates for remaining recoverable fossil fuels are bounded by two divergent estimates. David Rutledge an engineering professor at CalTech has calculated that we have about 560 billion tonnes of carbon in coal, oil and natural gas (Rutledge). A tonne of carbon is equivalent to about seven or eight barrels of oil for reference. Rutledge exhaustively researched historic production and applied a technique called Hubbard linearization, named for M. King Hubbard. In 1956 Hubbard famously and accurately forecast that the peak of United States oil production would occur in 1970 using this technique. Rogner estimates remaining recoverable reserves to be 5000 billion tonnes of carbon in all fossil fuels (Rogner). Both estimates are credible. All other credible estimates are between these bounds. The Intergovernmental Panel on Climate Change used values ranging from 1000 to 2000 billion tonnes.
If we assume that the fossil fuels we burn are limited by the Rutledge estimate, we can determine the best case scenario for our climate future. In this case world peak fossil fuels production will occur around 2024, in just 14 years as shown in figure 1. Robert Hirsch, Roger Bezdek and Robert Wendling analyzing peak oil estimated that we would need about 20 years to effect a transition to alternative sources of energy in order to avoid an economic recession (Hirsch). But their study is limited to oil production and they assumed that we would still have plenty of natural gas and coal. Vaclav Smil estimates we need at least one or two generations to effect a transition from fossil fuels (Smil). If these studies are correct and if Rutledge is right then we cannot avoid some level of economic collapse even if we go on a war footing. We need an energy and climate bill now. The recent election results preclude effective action for at least two years.
If we continue business as usual, i.e., no effective action, by 2024 the world population will be over 8 billion. All of these people will need to stay warm and cook their food. Since we are already deforesting our planet at a rate of 1.5 billion tonnes of carbon per year, it is rational to assume we will cut down every tree. There is a total of 288 billion tonnes of total carbon in our forests worldwide above ground (Moutinho). Therefore the minimum total emissions of carbon dioxide would be 848 billion tonnes. This is shown in figure 1. The climate is insensitive to the profile of our emissions. It is only the total that really counts.
I used Tom Wigley’s program (Wigley) to compute the accumulation of carbon dioxide in the atmosphere as a result, shown in figure 2. Note that even though emissions peak in 2024 in this scenario, atmospheric carbon dioxide continues to climb reaching 525 parts per million by volume about 40 years later. Significantly, according to Pelejero the threshold for coral survival is 450 parts per million by volume of carbon dioxide in the atmosphere (Pelejero). We will remain above that threshold for almost 300 years. Our oceans are becoming more acidic at a rate ten times faster than the Paleocene-Eocene Thermal Maximum which was a major marine extinction event (Pelejero). Combined with other ocean insults such as over fishing and pollution, even the lowest estimate of remaining fossil fuels, assuming we burn it all, results in a significant extinction event (Jackson).
Jeremy Jackson writes:
“We can summarize the extent of human impacts on the oceans in stark terms. Humans have caused and continue to hasten the ecological extinction of desirable species and ocean ecosystems. In their place, we are witnessing population explosions of formerly uncommon species and novel ecosystems with concomitant losses in biodiversity and productivity for human use. Many of the newly abundant species, such as jellyfish in the place of fish and toxic dinoflagellates in the place of formerly dominant phytoplankton, are undesirable equivalents to rats, cockroaches and pathogens on the land. Moreover, there are good theoretical reasons and considerable empirical evidence to suggest that, once established, such newly established communities become stabilized owing to positive feedbacks among newly dominant organisms and their highly altered environments—which raises questions about whether unfavourable changes can be undone if we put our minds to it.”
We will also denude our planet of trees as well as corals so the minimum credible estimate for remaining recoverable fossil fuels results in a major extinction event, which is already underway, and an economic catastrophe. Note that the real impact of even this minimal global warming is locked in after 2024. There will be no Mulligan.
In summary, we see that if Rutledge is right and we continue to elect the clueless, then we will suffer a very severe and prolonged depression and cause a serious extinction event. All other estimates result in more severe results.
In part 2, we will compare the results shown in figure 2 with the paleoclimate record to determine the resultant increase in surface temperature and sea level rise.
In part 3, I will lay out what we have to do to avoid catastrophe.
(Rutledge) Rutledge, D., 2007, http://rutledge.caltech.edu/ presentation and excel worksheet can be downloaded here. Rutledge, D. Hubbert’s peak, the coal question and climate change, APSO-USA World Oil Conference, 17-20 October 2007, Houston, Texas.
(Rogner) Rogner, H. H., An assessment of world hydrocarbon resources, Annual Review of Energy and the Environment, 22:217-262, 1997.
(Hirsch) Robert Hirsch, Roger Bezdek, Robert Wendling, Peaking Of World Oil Production: Impacts, Mitigation, & Risk Management, DOE Report, February 2005
(Smil) Vaclav Smil, Energy Transitions, 2010
(Wigley) Tom Wigley, http://www.cgd.ucar.edu/cas/wigley/magicc/
(Moutinho) Moutinho, P. and Schwatzman, S. (eds) Tropical deforestation and climate change, Belem, Brazil: Amazon Inst. For Environmental Research.
(Pelejero) Carles Pelejero, Eva Calvo and Ove Hoegh-Guldberg, “Paleo-perspectives on ocean acidification,” Trends in Ecology and Evolution Vol.25 No.6, March 2010.
(Jackson) Jeremy B. C. Jackson, “The future of the oceans past,” Phil. Trans. R. Soc. B (2010) 365, 3765–3778, doi:10.1098/rstb.2010.0278