A summary of the ‘Climate Departure’ research of Mora et al.
The video below contains a very compelling 22-minute summary of an impressive array of work, widely reported in the World’s newspapers this week. The research team, based in the Geography Department at the University of Hawaii, was led by Associate Professor Camilo Mora.
Sadly, it has already been dismissed by people with a track-record denying, downplaying or dismissing the nature, scale and urgency of the problem of anthropogenic climate disruption (ACD). People such as Bjorn Lomborg, for example.
A brief summary of the key points of the research:
1. For any geographic location the time of ‘climate departure’ is the time beyond which even the coldest monthly average temperature will be warmer than anything observed in the last 150 years. The same method was used to determine the time beyond which a range of other factors (such as precipitation and evaporation) would no longer fall below the range of local values observed in the last 150 years.
2. The monthly average data for all these calculations, data were obtained from 39 global climate models (GCMs – the accuracy of which I discuss below) constructed by 21 climate modelling centres in 12 different countries around the World. Common to all of these models is the same suite of CO2 emissions projections scenarios, two of which the research team used to define the range of possible temperature rises: RCP8.5 – representing a business as usual (BAU) scenario where humanity makes no attempt to reduce CO2 emissions; and RCP4.5 – representing a scenario where globally co-ordinated and concerted efforts are made to reduce CO2 emissions. With regard to atmospheric CO2 concentrations, it should be noted that:
– RCP8.5 is projected to result in a continuing increase to 900 ppm CO2 by the end of the Century; and
– RCP4.5 is projected to result in a peak value of 500 ppm being reached by mid-Century.
3. The results suggest that on average, climate departure (for temperature) is reached 2047 under the RCP8.5 scenario, or 2069 under the RCP4.5 scenario. This therefore implies that aggressive attempts to reduce carbon emissions could delay the onset of climate departure by several decades. Furthermore, the results suggest that climate departure will come to lower latitudes (equatorial and tropical areas) first. Under RCP8.5 this is as early as 2020 in some places. Under RCP4.5, climate departure is projected to be experienced almost everywhere by the end of the Century.
4. The team has produced an interactive map, published online here by the Washington Post newspaper, which can be used to see when climate departure is predicted under both scenarios for any location on the Earth’s surface.
5. The team suggests that the historical focus on absolute changes in temperature (i.e. predicted and observed to be greatest in polar regions) have given humans a false sense of security about the likely personal impacts. This study inverts that pattern and shatters the illusion that humans will not be directly impacted by changes in temperature. This is because, where the natural climate variability is smallest, less absolute change is required for it to be significant and most of the species present have less resilience to that change.
6. The research highlights the changes that have already occurred. Indeed, the most striking finding of the research is that the pH of seawater across the entire planet – i.e. without any exceptions – is already lower than it has been at any time in the last 150 years.
7. The research highlights the fact that those areas that are likely to reach climate departure soonest are also areas with the highest average population density and the lowest capacity to adapt. Under RCP4.5, it is expected that 1 billion people will be living in area experiencing unprecedented climatic conditions by 2050. Whereas, under the RCP8.5 this is expected to be 5 billion people (i.e. half the currently-projected global population).
8. The research indicates that the Earth’s most significant biological assets (essential ecosystem services and biodiversity) are at risk. This is the consequence of three facets of the above: (a) equatorial and tropical regions will be the first to experience climate departure; (b) they contain the greatest proportion of the Earth’s biological assets; and (c) are the least resilient to any change and the least able to adapt.
Conclusions (some readers may find some sentences upsetting)
1. If we stick to BAU, we will guarantee that (a) the long-term consequences will be increasingly unpleasant; (b) mitigation will become impossible; and (c) adaptation will be required sooner and faster and therefore be more costly. Alternatively, if we decide to try and mitigate ACD (by aggressively reducing CO2 emissions), we may be able to limit the unpleasantness and the scale and total cost of adaptation required (by humans and non-humans alike).
2. If we do nothing, the extinction of a significant proportion of species on Earth would appear to be unavoidable in the long-term (and, if that happens, the survival of humanity would have to be seriously in jeopardy). Alternatively, if we take action, the extinction of some species looks highly probable but, critically, this will buy most species several decades to adapt. This means that the costs of adaptation can be spread over those extra decades.
3. Given all of the above, how can it make any sense to continue to argue about what we should do?
Comments about the accuracy of Global Climate Models (GCMs)
One very easy way to dismiss all this is to point out that, in the course of the last decade, global average temperatures have slipped from well above 75th to just above 5th percentile of GCM predictions. Despite this, however, the exponential nature of the observed temperature increase over the last 150 years is very obvious in the above video.
Furthermore, the only way anyone can justify reaching the conclusion that this increase will not continue is by asserting that CO2 is not the main driver. A recent article on the Yale Forum on Climate Change and the Media website, entitled ‘Examining the Recent Slow-Down in Global Warming‘, has an excellent set of graphs that explain how and why we can be certain that CO2 is the main driver.
In addition, as per the comments I have posted on the above article, none of the GCMs include the global dimming effects of industrial pollution. Given that this is the case, I really do not understand why so many climate scientists keep saying we do not understand the reason for the current hiatus. In his book, ‘Storms of my Grandchildren’, James Hansen repeatedly complains about the fact that, 20 years ago, NASA refused to invest in satellite monitoring of this pollution. Thus we have been unable to model its effects because we have no data to put into the GCMs.