NERC research on 1.5°C global warming informs international special report on climate change
15 October 2018
The 2015 Paris climate agreement was a watershed moment for international action against climate change.
Global leaders from 195 countries committed to limit carbon emissions to keep global temperature rise well below 2°C (above the pre-industrial period) - with the aspiration to limit warming to 1·5°C. This would significantly reduce the risks and impact of climate change.
The agreement was a rallying call to nations, but it also posed many scientific questions. How reliable are the models we use to predict climate change? How much do we need to limit carbon emissions to still meet the 1·5°C target? And what are the impacts of sea-level rise, and biodiversity?
To approach these questions and more, NERC launched a research programme in partnership with the Department for Business, Energy & Industrial Strategy. The 'Understanding the Pathways to & Impacts of a 1·5°C Rise in Global Temperature' research aimed to advance our understanding of the research needs and provide timely evidence to inform policy following the introduction of the Paris agreement.
Today, research from the programme has been cited in the Intergovernmental Panel on Climate Change (IPCC) special report on 1·5°C warming, published internationally on 8 October 2018, and launched in the UK as part of Green Great Britain Week.
NERC Executive Chair Professor Duncan Wingham said:
NERC-funded research has played a central part in each of the published assessment reports from the IPCC, the cornerstones of international climate agreements, and this special report on 1·5 degrees warming is yet another example of the important role of UK environmental science in global efforts to mitigate the impacts of climate change.
Below is a summary of some of the NERC research programme's key findings:
No mitigating action could lead to a 4m rise in sea level by 2300.
Without mitigating for climate change, sea level could rise by about a metre this century. This research investigated the potential sea-level rise that we could see if we are able to keep global temperature rise below 1·5°C or 2°C by the end of the century - finding sea-level rise could be kept below 46cm and 54cm respectively. Taking no mitigating actions to reduce emissions could lead to a 4m rise in sea level by 2300, a scenario that would see major consequences for populations and ecosystems in coastal and lower lying areas worldwide.
Cited in the IPCC special report for 1·5°C warming, the research was part of the 'Sea level rise trajectories by 2200 with warmings of 1·5 to 2 degree C project' led by Dr Svetlana Jevrejeva at the National Oceanography Centre, with co-investigators at the University of Oxford.
We have 17 years left before we exceed the carbon budget to keep below 1·5°C.
Using a new approach to make predictions, researchers have estimated the total carbon budget for keeping global temperatures below 1·5°C. Their research shows that, at the current carbon dioxide emission rates, there are 17 years left before we have used up all the allowable carbon dioxide (CO2) emissions. This means that there is a very short window of time to develop the more carbon-efficient, and ultimately carbon-neutral, society needed to prevent warming above 1·5°C.
The project, 'Defining adjustable emission pathways to 1·5 degrees C warming, and assessing their feasibility, physical consequences and impacts', known as ADJUST 1·5, was led by Dr Phil Goodwin with co-investigators at the University of Southampton. Their research was cited in the IPCC special report for 1·5°C.
Current models have underestimated the uptake of CO2 by the ocean.
The ocean naturally captures and stores CO2 from the atmosphere, and this is factored into climate models. However, this research found evidence that, where we have been able to look, current models typically underestimate the recent and future increase in uptake of human-generated CO2 by the ocean. Researchers are now working to eliminate biases in the models we use to understand the global carbon budgets in the coming decades and beyond.
'CURB CO2: Carbon uptake revisited - Biases corrected using ocean observations' was led by Dr Paul Halloran with co-investigators at the University of Exeter.
Keeping warming below 1·5°C compared to 2°C is much better for biodiversity.
Limiting global warming to 1·5°C avoids half the risks associated with warming of 2°C for plants and animals, and two thirds of the risks to insects. Insects are particularly sensitive to climate change. At 2°C warming, 18% of insects studied are projected to lose more than half their geographical range, with the three major groups of insects responsible for pollination - vital to ensure global food security - shown to be especially sensitive to warming.
There is a significant benefit to keeping warming below 1·5°C compared to 2°C: in the former scenario, more species can keep up or even gain in range; if the latter, many species cannot keep up and far more species lose large parts of their range. Benefits occur everywhere but are greater in Southern Africa, the Amazon, Europe and Australia.
This research, 'Implications of the Paris agreement for biodiversity and conservation planning (IMPALA)', was led by Professor Rachel Warren at the University of East Anglia, and cited in the IPCC special report on 1·5°C warming.
Planting trees could be more effective than planting bioenergy crops.
The majority of scenarios showing we can limit warming to 1·5°C or 2°C are based on reducing CO2 emissions as well as removing carbon from the atmosphere, often using an approach of planting bioenergy crops coupled with carbon capture and storage (BECCS). However, plants naturally take up CO2 from the atmosphere and store it in biomass and soils, so increasing forest also results in CO2 removal. This research found that increasing forest area and conserving current forests could be more effective than a large-scale commitment to BECCS in meeting the Paris climate agreements, and that this is especially true if land is deforested to make way for bioenergy crops, which results in an overall loss of carbon from the land.
'Climate, land-Use and ecosystem services at 1·5°C' was led by Professor Peter Cox of the University of Exeter, with Dr Anna Harper at the University of Exeter and co-investigators at the Centre of Ecology & Hydrology and the University of Bristol.
Thawing permafrost and natural wetlands can make it more difficult to limit global warming.
A warmer climate will trigger more natural emissions of CO2 and methane from thawing permafrost and wetlands, on top of the emissions from burning of fossil fuels. These natural emissions have typically not been considered in previous assessments of the carbon budget. Taken in to account, allowable carbon emissions for limiting warming to 1·5°C are reduced by around 12%. This is equivalent to just over three years of human carbon emissions at 2017 emission rates. In the 2°C warming scenario, allowable carbon in reduced by 8·5%, equivalent to 4·4 years.
'Climate feedbacks from wetlands and permafrost thaw in a warming world (CLIFFTOP)' was led by Dr Garry Hayman at the NERC Centre of Ecology & Hydrology (CEH), with co-investigators at the CEH and the University of Leeds. Their research is cited in the IPCC special report on 1·5°C warming.
The remaining carbon budget is equivalent to less than 20 years of emissions at current levels.
In 2014, the IPCC made an assessment on the amount of CO2 emitted globally that would cause warming of 1·5°C by the end of the century. This research has shown that the remaining carbon budget is likely to be significantly more than assessed at the time of IPCC 5th report. The research found biases in the previous models and, once corrected, estimated the remaining carbon budget for 1·5°C is about 200 gigatonnes of carbon, equivalent to less than 20 years of emissions at current levels.
'Quantifying the cumulative carbon emissions consistent with a 1·5°C global warming (TCRE1·5)' was led by Professor Pierre Friedlingstein at the University of Exeter, with co-investigators at the University of Oxford. Research from the project is cited in the IPCC special report on 1·5°C warming.
Methane reduction could play significant role in achieving 1·5°C target.
Methane is a more potent greenhouse gas than CO2, so reducing methane emissions could make a substantial difference in our chances of meeting the Paris agreement targets by increasing the allowable carbon budget. Reducing methane emissions would also help lower concentrations of ozone gas in the atmosphere, which is harmful to plants, resulting in the vegetation being able to take more CO2 out of the atmosphere. This research concluded that early mitigation of methane emissions would significantly increase our chances of stabilising global warming below 1·5°C, alongside other benefits to human health and biodiversity.
The 'Methane, ozone, and the carbon budget for 1·5°C (MOC1·5)' research was led by Professor Bill Collins at the University of Reading, with co-investigators at the University of Exeter, and was cited in the IPCC Special Report on 1·5°C warming.
We can meet the Paris agreement targets through policy change, but only if we act fast.
It is possible to maintain warming to less than 1·5°C through stringent, but realistically achievable, policy measures, but only with rapid and urgent global action. However, the impact on the world's most sensitive ecosystems, such as the Arctic, could still be dangerously severe despite stringent carbon reduction policies that satisfy the goals of the Paris agreement.
Consumption of fossil fuels will decline in the near future, as a result of ongoing technological change, potentially exacerbated by new climate policies. This transition will result in clear winners, importers such as China and the EU, and losers, generally exporters such as Canada, the USA or Russia, which could see their fossil-fuel industries nearly shut down. If these countries keep up their investment and production levels despite declining demand, the impacts on their own economies will be worsened.
The 'Plausible policy pathways to Paris' project is led by Dr Neil Edwards of The Open University, and research from the project was cited in the IPCC special report on 1·5°C warming.
To read the full abstracts of all the projects, please visit our online grants browser - Grants on the Web - external link.
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1. NERC is the UK's main agency for funding and managing research, training and knowledge exchange in the environmental sciences. Our work covers the full range of atmospheric, Earth, biological, terrestrial and aquatic science, from the deep oceans to the upper atmosphere and from the poles to the equator. We coordinate some of the world's most exciting research projects, tackling major issues such as climate change, environmental influences on human health, the genetic make-up of life on Earth, and much more. NERC is part of UK Research & Innovation, a non-departmental public body funded by a grant-in-aid from the UK government.