Collection |

Targeting 1.5 °C

In December 2015, representatives from 195 nations met in Paris to negotiate an international agreement to combat climate change. The resulting ‘Paris Agreement’ codified an aspiration to limit the level of global temperature rise to 1.5 °C above pre-industrial levels —  lower than the previously generally agreed target of 2 °C. From a research standpoint, a more ambitious temperature target poses many questions that could draw scientific and intellectual attention and resources. Furthermore, the timescales in which researchers must decide how to engage with this new policy context is very short.

The Intergovernmental Panel on Climate Change has agreed to publish a special report on the costs and implications of the 1.5 °C target in 2018. In order to inform that process, researchers must decide which efforts to prioritise and begin work almost immediately. But deciding what can and should be delivered is far from trivial. This evolving collection draws together content from Nature Climate Change, Nature Geoscience, Nature Communications, Nature Energy and Nature to provide comment on how research might best inform decisions about limiting climate warming as well as presenting pertinent new research that addresses this very question.

Research

The Paris Agreement advocates that humanity should consider limiting global warming to no more than 1.5 degrees Celsius (°C) above pre-industrial temperatures, well below the previously discussed threshold of 2 °C. The announcement sparked a surge of research to understand the practicality and implications of the lower limit. Here, Philip Kraaijenbrink and colleagues simulate the effect of warming on the glaciers in the high mountains of Asia and show that, in a world that warms by just 1.5 °C, about 65 per cent of glacier mass will remain by 2100. But keeping warming below the 1.5 °C threshold is an ambitious goal. At the other extreme, scenarios that include continued high rates of greenhouse gas production instead suggest that only about 35 per cent of mass will remain by 2100.

Letter | | Nature

Nations are currently pursuing efforts to constrain anthropogenic warming to 1.5 °C. In such a world, model projections suggest the Arctic will be ice-free every one in forty years, compared to one in every five under stabilized 2 °C warming.

Article | | Nature Climate Change

Rising seas are a legacy of present and future climate change. Here the authors show that under the Paris Agreement, emissions in the next decades have a strong influence on the amount of sea level rise in the centuries to come, with the uncertainty dominated by ice-sheet contributions.

Article | Open Access | | Nature Communications

The populous global land monsoon region has been suffering from extreme precipitation. Here, the authors show that limiting global warming to 1.5 °C instead of 2 °C could reduce areal and population exposures to baseline once-in-20-year rainfall extremes by 25% (18–41%) and 36% (22–46%), respectively.

Article | Open Access | | Nature Communications

The scale and nature of energy investments under diverging technology and policy futures is of great importance to decision makers. Here, a multi-model study projects investment needs under countries’ nationally determined contributions and in pathways consistent with achieving the 2 °C and 1.5 °C targets as well as certain SDGs.

Article | | Nature Energy

Residual CO2 emissions from fossil fuels limit the likelihood of meeting the goals of the Paris Agreement. A sector-level assessment of residual emissions using an ensemble of IAMs indicates that 640–950 GtCO2 removal will be required to constrain warming to 1.5 °C.

Article | | Nature Climate Change

Land-based mitigation for meeting the Paris climate target must consider the carbon cycle impacts of land-use change. Here the authors show that when bioenergy crops replace high carbon content ecosystems, forest-based mitigation could be more effective for CO2 removal than bioenergy crops with carbon capture and storage.

Article | Open Access | | Nature Communications

Use of wood and crop residue for cooking and heating in rural China is a significant source of carbon emissions and air pollution. Using a survey of more than 34,000 households, researchers show that between 1992 and 2012 usage of these fuels decreased by much more than previous estimates, due primarily to rising incomes.

Article | | Nature Energy

COP21 led to a global commitment to decarbonization before 2100 to combat climate change, but leaves the timing and scale of mitigation efforts to individual countries. Here, the authors show that global carbon emissions need to peak within a decade to maintain realistic pathways for achieving the Paris Agreement.

Article | Open Access | | Nature Communications

Climate change is expected to alter ocean ecology, and to potentially impact the ecosystem services provided to humankind. Here, the authors address how rapidly multiple factors that affect marine ecosystems are likely to develop in the future ocean and the remedial effects climate mitigation might have.

Article | Open Access | | Nature Communications

While the photovoltaic industry aims to achieve cleaner energy production, it consumes energy and emits greenhouse gases during production and deployment. Here, Louwenet al. show that the industry has likely already reached break-even points for both greenhouse gases emissions and electricity consumption.

Article | Open Access | | Nature Communications

Prior mitigation assessments of atmospheric CO2 removal rely on bioenergy carbon capture and storage (BECCS), excluding bioenergy-biochar systems (BEBCS). Here, Woolf et al. find that BEBCS offers an alternative cost-effective solution, and may allow earlier CO2removal at a lower carbon price.

Article | Open Access | | Nature Communications

Review

Research and debate are intensifying on complementing CO2 emissions reductions with hypothetical climate geoengineering techniques. Here, the authors assess their potentials, uncertainties and risks, and show that they cannot yet be relied on to significantly contribute to meeting the Paris Agreement temperature goals.

Review Article | Open Access | | Nature Communications

Action needs to be taken to limit the impacts of climate change, however, human rights and the right to development need to be preserved. This Perspective weighs the risks of action and inaction on achieving a just transition to a low-carbon world.

Perspective | | Nature Climate Change

The principal climate goal of the Paris Agreement of December 2015 is to hold the increase in the global average temperature to well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 degrees above pre-industrial levels. This Perspective assesses the national plans submitted to the Paris meeting for post-2020 action to reduce global greenhouse gas emission by 2030. It also provides projections for global mean temperature increase over the twenty-first century that would be consistent with the present national plans and discusses options that may help to reduce greenhouse gas emissions to levels that are more consistent with maintaining a reasonable chance of meeting the well below 2 degrees Celsius climate target.

Perspective | | Nature

A long-term goal for climate policy can only be agreed through political processes, but science can inform these through mapping policy choices and the risks they create. Recommendations for the practical use of the IPCC's Fifth Assessment Report are provided.

Perspective | | Nature Climate Change

Opinion & Comment

Most scenarios to meet the Paris Agreement require negative emissions technologies. The EU has assumed a global leadership role in mitigation action and low-carbon energy technology development and deployment, but carbon dioxide removal presents a serious challenge to its low-carbon policy paradigm and experience.

Comment | | Nature Energy

Although nearly all 2 °C scenarios use negative CO2 emission technologies, only relatively small investments are being made in them, and concerns are being raised regarding their large-scale use. If no explicit policy decisions are taken soon, however, their use will simply be forced on us to meet the Paris climate targets.

Comment | | Nature Energy

Nation states need to incentivize negative emissions technologies if they are to take the decarbonization of whole energy systems seriously. This incentivization must account for public values and interests in relation to which technologies to incentivize, how they should be incentivized and how they should be governed once incentivized.

Comment | | Nature Energy

Temperature overshoot scenarios that make the 1.5 °C climate target feasible could turn into sources of political flexibility. Climate scientists must provide clear constraints on overshoot magnitude, duration and timing, to ensure accountability.

Comment | | Nature Geoscience

The remaining carbon budget consistent with limiting warming to 1.5 °C allows 20 more years of current emissions according to one study, but is already exhausted according to another. Both are defensible. We need to move on from a unique carbon budget, and face the nuances.

Comment | | Nature Geoscience

The Intergovernmental Panel on Climate Change is preparing a report on keeping global warming below 1.5 °C. How the panel chooses to deal with the option of solar geoengineering will test the integrity of scientific climate policy advice.

Commentary | | Nature Geoscience

The Paris Agreement introduced three mitigation targets. In the future, the main focus should not be on temperature targets such as 2 or 1.5 °C, but on the target with the greatest potential to effectively guide policy: net zero emissions.

Commentary | | Nature Geoscience

Stéphane Hallegatte, Katharine J. Mach and colleagues urge researchers to gear their studies, and the way they present their results, to the needs of policymakers.

Comment | | Nature

The Paris Agreement duly reflects the latest scientific understanding of systemic global warming risks. Limiting the anthropogenic temperature anomaly to 1.5–2 °C is possible, yet requires transformational change across the board of modernity.

Commentary | | Nature Climate Change

The adoption of the Paris Agreement is a historic milestone for the global response to the threat of climate change. Scientists are now being challenged to investigate a 1.5 °C world — which will require an accelerated effort from the geoscience community.

Commentary | | Nature Geoscience