Back to Sustainable Energy Transition: Scenarios and Progress

The IPCC’s original charge is as follows:

The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for the assessment of climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988 to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts. In the same year, the UN General Assembly endorsed the action by WMO and UNEP in jointly establishing the IPCC.

The IPCC is a scientific body under the auspices of the United Nations (UN). It reviews and assesses the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change. It does not conduct any research nor does it monitor climate related data or parameters.

As the section above states, the IPCC does not do any research of its own. It is charged with reviewing and assessing ongoing research. It is also a very strong advocacy organization that is trying to influence policy makers to agree on policies that will prevent future global environmental disaster in the form of climate change. The first requirement for persuading somebody, though, is to have them actually read what you write. Right now, I strongly suspect (though I have no express evidence) that very few policy makers read what the IPCC writes directly. Instead, most policy makers, along with the general public, get their information about the IPCC’s findings as filtered through intermediaries such as press reports. The press, in turn, only presents a few very short highlights; this is only one of the vast number of news issues it covers. The IPCC’s data is in direct competition with all of the other sources of information. This mode of information distribution makes it relatively easy for people (deniers!) presenting counter-arguments to make their voices heard loudly, no matter how solid the science is supporting anthropogenic (man-made) climate change. This continues to be the case, in spite of the fact that the IPCC reports include specific chapters directed at “policy makers.” In fact, very few policy makers can follow these chapters (see my October 14, 2014 blog). One big factor is the way that the IPCC presents the future: in terms of scenarios.

I showed this graph in my last two blogs, and am including it again here. It was one of the main highlights of the latest IPCC report; it describes the historical and projected global average surface temperature changes.

IPCC Global average surface temperature change

In its August 14th report, Skeptical Science gave a simplified description of the various IPCC scenarios (again with the intermediaries!). Here is a key section:

Why are scenarios necessary?

“Scenarios of different rates and magnitudes of climate change provide a basis for assessing the risk of crossing identifiable thresholds in both physical change and impacts on biological and human systems.”

Source: “Towards New Scenarios for Analysis of Emissions, Climate Change, Impacts, and Response Strategies”, IPCC Technical Summary, 2007

There are many climate modelling teams around the world. If they all used different metrics, made different assumptions about baselines and starting points, then it would be very difficult to compare one study to another. In the same way, models could not be validated against other different, independent models, and communication between climate modelling groups would be made more complex and time-consuming.

Another problem is the cost of running models. The powerful computers required are in short supply and great demand. Simulation programming that had to start from scratch for each experiment would be wholly impractical. Scenarios provide a framework by which the process of building experiments can be streamlined.

In order to address these issues, in 1992 the Intergovernmental Panel on Climate Change (IPCC) published the first set of climate change scenarios, called IS92. In year 2000 the IPCC released a second generation of projections, collectively referred to as the Special Report on Emissions Scenarios (SRES). These were used in two subsequent reports; the Third Assessment Report (TAR) and Assessment Report Four (AR4) and have provided common reference points for a great deal of climate science research in the last decade.

In 2007, the IPCC responded to calls for improvements to SRES by catalysing the process that produced the Representative Concentration Pathways (RCPs). The RCPs are the latest iteration of the scenario process, and are used in the next IPCC report – Assessment Report Five (AR5) in preference to SRES.

The changes from the SRES to the RCP scenarios in the last report were introduced mainly for the benefits of scientists, to make “reviewing and assessing” easier. In the process, SRES scenarios’ close connections with socioeconomic changes got lost in favor of a focus on the net impact on greenhouse gas emissions. Meanwhile, the number of evaluated scenarios changed: in both the SRES and the RCPs, there were four families, but the SRES included 40 scenarios, whereas the RCPs are defined in terms of only four different emission scenarios.

In terms of the above RCP8.5 scenario, which depicts an everlasting increase in temperature, the new focus makes very little difference. It basically shows the “business as usual” scenario or, using the new terminology: the “background scenario.” In all presentations, this is the scenario that we all start with; one extrapolated from a future with no change in the rates of growth, or the associated emissions.

The big difference is in showing how we are trying to get to where we want to be – the “environmentally stable” RCP2.6 scenario. The authors in the journal “Climatic Change” (November 2011, Volume 109, Issue 1-2,) give a detailed account of the considerations behind this scenario. The SRES and RCP scenario families are both “what ifs” based on plugging possible socioeconomic inputs into computers to calculate greenhouse gas emission consequences. The SRES scenario family represents passive scenarios, while the RCP family is constructed to include mitigation policies. It is obvious that the RCP2.6 requires much stronger mitigation policies compared to RCP8.5, which describes what will happen if we continue what we are doing now. To have any effect, mitigation policies require global agreement, and that is very hard to come by – especially now. In spite of the difficulties, there is continuing global progress to close the gap between the two scenarios. Future blogs will try to go into some details of what must take place to narrow the gap.

About climatechangefork

Micha Tomkiewicz, Ph.D., is a professor of physics in the Department of Physics, Brooklyn College, the City University of New York. He is also a professor of physics and chemistry in the School for Graduate Studies of the City University of New York. In addition, he is the founding-director of the Environmental Studies Program at Brooklyn College as well as director of the Electrochemistry Institute at that same institution.
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