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A dose of realism in environmental research

Climate and environmental issues evoke strong responses in the world today. The range of reactions covers everything from “There are no problems” to “The world is ending.” However, we intuitively know the final answer rests somewhere in the middle of the extremes. But, how do we determine what a reasonable prediction for the future is? 

Environmental science is rife with probability analysis, and for good reasons because environmental research always involves the study of complex systems. End answers are inevitably the result of modeling a multitude of variables. So, modeling of these complex systems requires that researchers make assumptions on how important a given variable is and what range of values might best represent that variable.  

This uncertainty does not imply that models are unreliable. Rather, it demonstrates that the model’s ultimate value rests on its ability to predict a realistic range of outcomes, and to quantify how probable any individual outcome is. This range of probable outcomes defines which outcomes are likely to happen and which outcomes are unlikely. 

If I flip a coin ten times, I will likely get heads about five times. However, getting a heads outcome ten times in ten flips is highly unlikely. A global warming model may give an outcome range that includes cooling at one extreme and a 10-degree temperature rise at the other extreme. But, the most important information for future planning is the most-likey case, not the two end-member extremes. 

Global Warming and RCPs

Relative Concentration Pathways (RCPs) are the scenarios for climate warming developed for use in the 2014 IPCC Fifth Assessment Report. Individually they represent discrete scenarios, but collectively they project a range of possible outcomes for global warming. 

One of these scenarios, RCP2.6, became famous under the 2015 Paris Climate Agreement.  This scenario described a set of conditions that kept global warming below 2 degrees Celsius as compared to pre-industrial temperatures. RCP2.6’s fame arose from the fact that the Paris Agreement signatories pledged to work towards a goal of limiting global temperature rise to 2 degrees Celsius. Indications now are that this goal is more fantasy than reality. 

Another model, RCP8.5, investigated the conditions required for a 5 degree Celsius temperature rise by the end of the century. This scenario assumes a heavily fossil-fuel dependent future with no meaningful world government policies to mitigate the effects of massive fossil-fuel emissions.   

RCP2.6 and RCP8.5 represent unlikely outcomes that are more on the extremes of the range than near the middle. The world is only five years into the Paris Agreement, and indications are that the conditions for succeeding with RCP2.6 are not being met. However, that does not immediately catapult us into the bleak dystopian future of RCP8.5.  Environmental research reveals far more likely futures.

Most likely warming

Future projections from the International Energy Agency (IEA) show a “likely” case supporting a 3 degree Celsius rise over the next 80 years. This increase in average global temperature will then take the planet to “hot earth” conditions. But the earth avoids the more severe conditions that come with a 5 degree Celsius temperature rise. 

The IEA modeling shows a range of global warming outcomes ranging from 1.5 degrees to 5 degrees. Continued work in improving data quality and refining modeling techniques will allow greater confidence in environmental research as time passes. But, for now, planning for a rise of 3 degrees Celsius seems to be a reasonable approach. 

Keeping the rise of global temperatures to under 3 degrees, therefore requires that world-wide government policy become more proactive in combating fossil fuel emissions. But politics, being what it is, requires that this path be supported by a ground-swell of social activism that is currently lacking. If you are fortunate enough to live in a country where voters elect their leaders, then do your part and vote for the future you want.


Embrace a Hot Earth (Source: ArcheanWeb) – Also:


Emissions – the ‘business as usual’ story is misleading (By Zeke Hausfather & Glen P. Peters; Nature) – Also:

Feature Image: Sunny green paddy fields with trees and long shadows at golden hour. (By Basile Morin) & Dead fish on coast. (By Hillebrand Steve, U.S. Fish and Wildlife Service) (Modified) – This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license –

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.