The Intergovernmental Panel on Climate Change, or IPCC, has released the Summary for Policymakers of the Special Report on Global Warming of 1.5 degrees Celsius.

Diana Liverman, a University of Arizona Regents’ Professor in the School of Geography and Development in the College of Social and Behavioral Sciences, is one of the authors of the overall report and of the Summary for Policymakers.

The IPCC press release states: “Limiting global warming to 1.5 degrees C would require rapid, far-reaching and unprecedented changes in all aspects of society. With clear benefits to people and natural ecosystems, limiting global warming to 1.5 degrees C compared to 2 degrees C could go hand in hand with ensuring a more sustainable and equitable society.”

The report was invited by governments when they adopted the Paris Agreement in December 2015 to combat climate change. Nations agreed to reduce emissions of greenhouse gases in order to hold the increase in global average temperature to well below 2 C above pre-industrial levels and pursue efforts to limit the increase to 1.5 C.

“The report shows that the current Paris commitments to reduce emissions are inadequate," Liverman said. "They asked us to compare 1.5 C and 2 C of warming, but the current Paris commitments could take us to more than 3 C of global warming by 2100. Because land warms more than oceans, this could result in average temperatures more than 4 C (7 F) warmer than at present in Arizona.”

The IPCC report, known as SR15, examines the latest science on climate change and its impacts and assesses the chances of keeping temperatures under 1.5 C global warming, compared to 2 C. It also looks at how efforts to limit warming interact with sustainable development. The report will be the main scientific input to the Climate Change Conference (COP24) this December in Katowice, Poland.

The overall report has five chapters and 91 authors and review editors from 40 countries. Liverman is one of five U.S. authors of the Summary for Policymakers. She was a lead author for the full report’s fifth chapter on sustainable development, poverty eradication and reducing inequalities, which was coordinated by UA Arid Lands alumna Petra Tschakert. Liverman also contributed to cross-chapter boxes on food security, solar radiation management and sustainable development.

The IPCC 48^th Session, held Oct. 1-5 in Incheon, Republic of Korea, brought the authors together with government delegates to negotiate the final wording of the Summary for Policymakers. Liverman focused on sections related to climate adaptation and the relationship between climate and sustainable development.

Limiting Warming to 1.5 C Will Be Challenging

The IPCC reports that the world will need to make very steep cuts in emissions and look for every opportunity for carbon dioxide removal to have any chance of limiting warming to 1.5 C  above pre-industrial levels. Global net human-caused emissions of carbon dioxide must be reduced from 2010 levels by 45 percent by 2030 and reach “net zero” around 2050. Global warming is likely to reach 1.5 C between 2030 and 2052 if emissions continue to increase at the current rate.

“In order to get near 1.5 C or 2 C, we have to not just reduce emissions, but also consider negative emissions,” Liverman said. “We’ve got to make sure that the biosphere is taking up as much carbon dioxide  as possible, which means maintaining and expanding forests and other land uses that sequester carbon.”

Human activity is estimated to have already caused approximately 1 C of warming, with negative impacts on people, ecosystems and livelihoods.

Warming above 2 C is anticipated to impede economic growth and increase poverty and disease as countries struggle with the impact of severe weather, such as floods, hurricanes, droughts and heat waves.

Although the report didn’t specifically address the impact of 1.5 C and 2 C to the southwestern United States, Liverman said the report has implications for the region.

“Limiting warming to 1.5 C would reduce the impacts of global warming on ecosystems, water resources and heat waves on the southwestern United States compared to 2 C,” she said. “Our region can also contribute to the ambitious emission reductions needed to limit warming, especially through rapid implementation of solar, land use management and higher energy efficiency.”

Impacts on Sustainable Development and Adaptation

SR15 is the first IPCC report since the United Nations established the sustainable development goals, or SDGs, in 2015. Liverman and her colleagues were asked to look at impacts of global warming of 1.5 C and 2 C on sustainable development goals such as eradicating poverty and hunger, and maintaining people’s health. 

The summary report states that “limiting global warming to 1.5 C compared to 2 C could reduce the number of people both exposed to climate-related risks and susceptible to poverty by up to several hundred million by 2050.”

Liverman said that warming to 2.0 C degrees would have some fairly serious implications for the achievement of sustainable development goals, because higher levels of warming will negatively affect food security, increase health risks, cause losses of biodiversity and flood coastal cities.

“At 1.5 C you would find some pretty serious impacts, but they would be considerably less than at 2 C, especially for biodiversity and health,” Liverman said. “For example, coral reefs would disappear at 2 C, but some would survive at 1.5 C. Adaptation needs and costs, such as protecting agriculture and coasts, would be higher at 2 C than at 1.5 C.”

Liverman and her colleagues also looked at how efforts to respond to global warming might impact sustainable development.

“Getting to 1.5 C requires such ambitious emission reductions that some of the things that might need to be done could have negative implications for development goals,” Liverman said. “For example, there could be trade-offs between bioenergy production, and goals to reduce hunger and protect ecosystems.”

The scientists also found that if not carefully implemented, adaptation even to 1.5 C could have negative impacts for some people and ecosystems – adaptation projects that do not include or benefit women or indigenous people, for example.

Scientific Assessments of Climate Change

The IPCC, a group representing over 195 governments, was established by the U.N. Environment Programme and the World Meteorological Organization in 1988 to provide policymakers with regular scientific assessments concerning climate change.

"The IPCC assessments are not only instrumental in informing policy for governments around the world, but they are also useful in identifying priorities for researchers working in climate and related fields," Liverman said. "It's a testament to the UA's strong climate research focus that we have a long history of involvement in IPCC and in filling key knowledge gaps identified in their assessments."

While Liverman was in South Korea, she met with the newly formed IPCC Gender Task Force. Liverman is the group’s rapporteur, or the person who reports on its meetings. Liverman and Miriam Gay-Antaki, who recently received her Ph.D. from the UA School of Geography and Development, authored "Climate for Women in Climate Science: Women Scientists and the Intergovernmental Panel on Climate Change."

Liverman, whose research focuses on the human dimensions of global environmental change, was involved in the IPCC assessments in 1995 and 2001 and will be a review editor for the 2021 sixth assessment. She has been an active member of national and international advisory committees on global change, including the U.S. NAS Committee on the Human Dimensions of Global Environmental Change and the Inter American Institute for Global Change Research.

Previously co-director of the UA Institute of the Environment, Liverman now leads a UA College of Social and Behavioral Sciences initiative on sustainable development and environment, which is focused on the role of the social sciences in solving the grand challenges of sustainable development.

For more information on the Summary for Policymakers of the Special Report on Global Warming of 1.5 degrees Celsius, visit www.ipcc.ch.