The world is unlikely to reach the ‘worst-case scenario’ of climate change by the end of the century, according to a new study, that found efforts to reduce emissions are helping keep warming under control.
The Paris Climate Agreement goal to limit global warming this century to 3.6 degrees Fahrenheit over preindustrial temperatures was set in December 2015.
This urged nations to take action to reduce emissions of greenhouse gasses in order to forestall the most extreme climate change scenarios being predicted by scientists at the time – that could see temperatures rise by up to 9 degrees Fahrenheit.
However, a new study by the University of Colorado Boulder, which looked at the latest data on emission levels, found those extreme temperatures that would have led to a sharp rise in extreme weather events and sea rises are no longer plausible.
The researchers found that the extreme scenarios and temperature increase predictions were based on outdated data from 15 years ago, that didn’t take into account recent efforts to reduce emissions, and a move to renewable energy.
They said that temperatures are likely to rise by no more than 4 degrees Fahrenheit by 2100, and the 3.6F goal ‘is still within reach’ if emission reduction continues.
They warned a rise of 3.6F would still place a ‘significant toll on the planet’, as it was a global average, with some areas of the world ‘much warmer’ and others colder.
Published in the journal Environmental Research Letters, the new study explored the most recent global emission data and created new models to predict likely climate change scenarios over the next 78 years.
They found that by 2100, temperatures are likely to be between 3.6F and 5.4F warmer than pre-industrial levels, with an average of 3.96F.
‘This is cautiously optimistic good news with respect to where the world is today, compared to where we thought we might be,’ said lead author Roger Pielke Jr., professor of environmental studies.
‘The two-degree target from Paris remains within reach,’ he added, and it is thanks to efforts by nations to reduce emissions.
Almost every nation on Earth signed the Paris Climate Agreement in 2015, aiming to keep emissions below 3.6F, but trying to keep them below 2.7F.
While the upper target is ‘within reach’ it will still require significant effort, including leaving unexplored fossil fuels in the ground – rather than exploiting them.
To predict what impact emissions will have on future global temperatures, researchers create scenarios.
These are forecasts of how the future might evolve based on factors such as projected greenhouse gas emissions and different possible climate policies.
The most commonly used scenarios, called the Representative Concentration Pathways (RCPs), were developed by the IPCC starting in 2005.
The Shared Socioeconomic Pathways (SSPs) that followed, starting in 2010, were meant as an update. These ‘pathways’ are made up of hundreds of scenarios, with a selection of about 11 used to inform IPCC climate reports.
Pielke and colleagues compared the scenarios used for the IPCC reports to the projected 2005-2050 fossil fuel and industry carbon dioxide emissions growth rates that were most consistent with real-life observations from 2005-2020.
Comparing scenarios with predictions from real word carbon emissions gave them a fresh insight into just how plausible the predictions were.
They found that there were between 100 and 500 scenarios, out of the more than 1,100, that most closely matched emission projections.
These scenarios represent what futures are plausible if current trends continue, but also take into account climate policies adopted, or promised to be adopted by countries to reduce carbon emissions.
While their study finds that the most extreme scenarios are unlikely, and we could be on target for 3.6F of warming, more optimistic or pessimistic futures could also exist.
‘Because we haven’t updated our [IPCC] scenarios [for many years], there are also some futures which are plausible but haven’t yet been envisioned,’ said Pielke Jr.
However, their findings join other studies that suggest we are no longer headed for the worst-case scenario of climate change, including the IPCC Sixth Assessment Report released last year.
The reason for the sudden ‘good news’ is because models and scenarios used to make the predictions are getting old, with most developed more than a decade ago.
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