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Science Alert: Experts Respond

Climate effects from burning all remaining fossil fuels – Expert reaction

Posted in Science Alert: Experts Respond on May 25th, 2016.

Burning the Earth’s remaining fossil fuels could lead to a bigger global temperature increase than expected, a new study finds.

earth-from-space-cloudsIf we were to use up all of our planet’s fossil fuel resources, we’d increase the global average temperature by about 8°C globally by 2300, Canadian scientists report in Nature Climate Change.

The scientists say that other Earth system models, which are not as comprehensive or complex as theirs, are underestimating how much warming we’ll get.

The researchers also estimate that we’ll also see a more severe temperature rise of about 15-20°C in the Arctic regions, four times more rain in the tropical Pacific, and half the amount of rain in Australia by 2300.

Read more about the  research on

The SMC collected the following expert commentary.

Dr Sam Dean, Chief Scientist – Climate, Atmosphere and Hazards, NIWA, comments:

“The current concentration of CO2 in the atmosphere is now around 400 parts per million (ppm). In the scenario considered in this paper, the atmosphere reaches a concentration of about 2000 ppm, an increase of 5 times the current amount. This is achieved by burning most of the available fossil fuel reserves over the next 200 years or so. It assumes that the people of the world take no action to mitigate the use of fossil fuels as an energy source and do not change behaviour in response to increasing temperatures. As such it represents a ‘worst case scenario’.

“The authors make use of sophisticated Earth Systems models that were used in the Fifth Assessment Report of the IPCC. The warming seen in these models can be taken as our current best estimate of what will happen if this event actually occurs. One of the reasons for this is that they incorporate many of the key feedbacks in the climate system that are important over such long time scales. The warming of between 6.4-9.5 degrees by the year 2300 is greater in these models than in simpler models previously used for such analysis, and this is the primary finding in the work.

“It should be noted that warming would continue to increase long after 2300, as the planet continued to adjust to such high levels of CO2. In the recently negotiated Paris Agreement the nations of the world committed to ‘holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C’.

“It is unsurprising that the greatest warming occurs in the Arctic in these models, due to a process called ‘polar amplification’. Snow and ice are white, and as a result are strong reflectors of solar radiation. Warmer temperatures in the Arctic melt snow and ice exposing the darker ocean and land to increased heating, and this then amplifies the increase in air temperature in a runaway effect.  The Antarctic would ultimately suffer the same fate, but this happens more slowly because of the significant time it will take to melt the large ice sheets covering the Antarctic continent.”

Prof James Renwick, School of Geography, Environment and Earth Sciences, Victoria University of Wellington, comments:

“The estimate is realistic, given the physical processes included in the models analysed. The results are consistent with results shown in the last IPCC report, where the extended scenario “RCP8.5” – the one where we just keep burning the fossil fuels – showed warming of 8 or 9 degrees by 2300. The estimates in this paper are realistic – and very worrying. An average warming of around 8°C would take the climate into a vastly different state.

“[The Arctic has a more extreme temperature increase because] This is a symptom of what’s called “polar amplification”, where the poles warm much faster that the global average. One of the main processes is the feedback between ice/snow and warming. In the Arctic, a little warming leads to some melt of snow and loss of sea ice over the ocean. Since snow/ice is white and very reflective, while the land or ocean underneath is much darker, then net result is increased absorption of sunlight where the snow and ice has melted. This heats the Arctic land and ocean surface, leading to more melt, and so on. Eventually, this will also happen over the Antarctic and southern oceans, but because there’s so much very thick ice on the continent of Antarctica, the accelerated warming takes a lot longer to get going.

“[The paper estimates climate change as far ahead as 2300 rather than 2100] Because the greenhouse gas emissions scenario assumed that it would take that long to burn all the coal and oil. We are unlikely to emit that much carbon dioxide by 2100, but it could be done within 250 or 300 years.

“This paper is based on analysing some of the climate models used in the last IPCC report, so these results – based on an aggregate of four “earth system models” – are entirely consistent with earlier results. One interesting feature of this work is to demonstrate that the earth system models that include aspects of the carbon cycle as well as the full ocean and atmospheric circulation, project more warming than do the simpler models often used for very long-term projections. We need to consider all physical processes to get a good handle on what the future holds, especially over longer time horizons.

“The paper is consistent with our understanding of how the climate responds to large injections of greenhouse gases, and gives a stark warning of what the future could hold if we let fossil fuel burning continue unabated. The amount of warming and climate change shown by these results would throw global society into chaos and would likely result in billions of deaths, from hunger and conflict over resources.”

Dr Jim Salinger, Honorary Research Fellow, Department of Geography, University of Otago, comments:

“This paper is a salutary reminder that this is the critical decade in which the rubber needs to hit the road in terms of the Paris Climate Agreement.

“According to US government climate monitoring agencies, April 2016 is the 12th consecutive month of record global temperatures with 2016 most likely to be the warmest on record – as global warming accelerates.

“Governments of the world need to ratify the Paris Agreement as soon as possible and ratchet up their mitigation of greenhouse gas mitigation plans provided. The Paris agreement is the opportunity to be used by all nations collectively. There is no time to lose, otherwise dangerous climate change will be here later this century.”

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