International climate change agreements typically specify global warming thresholds as policy targets, but the relative economic benefits of achieving these temperature targets remain poorly understood. Uncertainties include the spatial pattern of temperature change, how global and regional economic output will respond to these changes in temperature, and the willingness of societies to trade present for future consumption. Here we combine historical evidence with national-level climate and socioeconomic projections to quantify the economic damages associated with the United Nations (UN) targets of 1.5 °C and 2 °C global warming, and those associated with current UN national-level mitigation commitments (which together approach 3 °C warming). We find that by the end of this century, there is a more than 75% chance that limiting warming to 1.5 °C would reduce economic damages relative to 2 °C, and a more than 60% chance that the accumulated global benefits will exceed US$20 trillion under a 3% discount rate (2010 US dollars). We also estimate that 71% of countries—representing 90% of the global population—have a more than 75% chance of experiencing reduced economic damages at 1.5 °C, with poorer countries benefiting most. Our results could understate the benefits of limiting warming to 1.5 °C if unprecedented extreme outcomes, such as large-scale sea level rise, occur for warming of 2 °C but not for warming of 1.5 °C. Inclusion of other unquantified sources of uncertainty, such as uncertainty in secular growth rates beyond that contained in existing socioeconomic scenarios, could also result in less precise impact estimates. We find considerably greater reductions in global economic output beyond 2 °C. Relative to a world that did not warm beyond 2000–2010 levels, we project 15%–25% reductions in per capita output by 2100 for the 2.5–3 °C of global warming implied by current national commitments, and reductions of more than 30% for 4 °C warming. Our results therefore suggest that achieving the 1.5 °C target is likely to reduce aggregate damages and lessen global inequality, and that failing to meet the 2 °C target is likely to increase economic damages substantially.
Stanford scientists found that the global economy is likely to benefit from ambitious global warming limits agreed to in the United Nations Paris Agreement.
Failing to meet climate mitigation goals laid out in the U.N. Paris Agreement could cost the global economy tens of trillions of dollars over the next century, according to new Stanford research. The study, published in Nature, is one of the first to quantify the economic benefits of limiting global warming to levels set in the accord.
The agreement commits 195 countries to the goal of holding this century’s average temperature to 2 degrees Celsius above levels in the pre-industrial era. It also includes an aspirational goal of pursuing an even more stringent target of limiting temperature rise to 1.5 degrees. To date, the economic benefits of achieving these temperature targets have not been well understood.
“Over the past century we have already experienced a 1-degree increase in global temperature, so achieving the ambitious targets laid out in the Paris Agreement will not be easy or cheap. We need a clear understanding of how much economic benefit we’re going to get from meeting these different targets,” said Marshall Burke, assistant professor of Earth system science in the School of Earth, Energy & Environmental Sciencesand lead author of the study.
To develop this understanding, a team of Stanford researchers studied how economic performance over the past half-century correlated with changes in temperature around the world. Then, using climate model projections of how temperatures could change in the future, they calculated how overall economic output is likely to change as temperatures warm to different levels.
The researchers found a large majority of countries – containing close to 90 percent of the world’s population – benefit economically from limiting global warming to 1.5 degrees instead of 2 degrees. This includes the United States, China and Japan – the three largest economies in the world. It is also true in some of the world’s poorest regions, where even small reductions in future warming generate a notable increase in per capita gross domestic product.
“The countries likely to benefit the most are already relatively hot today,” said Burke. “The historical record tells us that additional warming will be very harmful to these countries’ economies, and so even small reductions in future warming could have large benefits for most countries.”
The projected costs from higher temperatures come from factors such as increases in spending to deal with extreme events, lower agricultural productivity and worse health, the scientists said.
Previous research has shown that the actual climate commitments each country has made as part of the Paris Agreement add up to close to 3 degrees of global warming, instead of the 1.5–2 degrees warming goals.
Given this discrepancy, the researchers also calculated the economic consequences of countries meeting their individual Paris commitments, but failing to meet the overall global warming goals of 1.5–2 degrees. They found that failing to achieve the 1.5–2 degrees goals is likely to substantially reduce global economic growth.
Percentage gain in GDP per capita in 2100 from achieving 1.5 degrees Celsius global warming instead of 2 degrees.
Percentage gain in GDP per capita in 2100 from achieving 1.5 degrees Celsius global warming instead of 2 degrees. (Image credit: Marshall Burke)
“It is clear from our analysis that achieving the more ambitious Paris goals is highly likely to benefit most countries – and the global economy overall – by avoiding more severe economic damages,” said Noah Diffenbaugh, professor of Earth system science and paper co-author.
The authors note the study may underestimate the total costs of higher levels of global warming. That’s especially true if catastrophic changes such as rapid melting of the ice on Greenland or Antarctica come to pass, or if extreme weather events such as heatwaves and floods intensify well beyond the range seen in historical observations. A recent studyby Diffenbaugh and his colleagues showed that even with reduced levels of global warming, unprecedented extreme events are likely to become more prevalent.
The new research helps shed light on the overall economic value of the Paris Agreement, as well as on the Trump administration’s decision to withdraw the U.S. from the accord because of concerns that it is too costly to the U.S. economy. The researchers calculated that the overall global benefits of keeping future temperature increases to 1.5 degrees are likely in the tens of trillions of dollars, with substantial likely benefits in the U.S. as well. They note that these benefits are more than 30 times greater than the most recent estimates of what it will cost to achieve the more ambitious 1.5 degrees goal.
“For most countries in the world, including the U.S., we find strong evidence that the benefits of achieving the ambitious Paris targets are likely to vastly outweigh the costs,” said Burke.
Burke is also a fellow at the Center on Food Security and the Environment, the Stanford Woods Institute for the Environmentand the Freeman Spogli Institute for International Studies. Diffenbaugh is also the Kara J Foundation Professor, the Kimmelman Family Senior Fellow in the Stanford Woods Institute for the Environment and an affiliate of the Precourt Institute for Energy. Additional co-authors include W. Matt Davis, a former researcher at the Center on Food Security and the Environment. The research was supported by the Erol Foundation.
Media Contacts
Marshall Burke, School of Earth, Energy & Environmental Sciences: mburke@stanford.edu, (650) 721-2203 Noah Diffenbaugh, School of Earth, Energy & Environmental Sciences: diffenbaugh@stanford.edu, (650) 223-9425 Michelle Horton, Center on Food Security and the Environment: mjhorton@stanford.edu, (650) 498-4129
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The three largest economies in the world and almost 90 percent of the global population benefit economically from limiting global warming to 1.5 degrees instead of 2 degrees. | iStockphoto/leolintang
This report was produced for the Abe Fellows Global Forum 2017 symposiums on climate change, held in partnership with Stanford University's Walter H. Shorenstein Asia Pacific Research Center (Abe Global | Stanford, October 20, 2017) and the Asia Society Texas Center (Abe Global | Houston, October 18, 2017), respectively.
Energy-intensive production has been both a leading contributor to climate change as well as one of the keys to modern economic growth over the last several centuries. In the post-WWII era, the “economic miracles” of Asian growth—starting with Japan, and followed by South Korea, Taiwan, China, and now increasingly India—have lifted hundreds of millions of people out of poverty. At the same time, these “economic miracles” have created huge pollution problems which have adversely affected the health of millions of people while speeding up the effects of climate change.
Some early developers from this group—including Japan—have made efforts to clean up their air and water, created more energy efficient economies, lowered their carbon footprints and contributed to initiatives to slow global warming. The Fukushima nuclear power plant disaster forced Japan to take even more aggressive action to reduce energy consumption and lessen its impact on the global environment. In contrast, the United States, as a sizeable nation-state both in its geographic area and economy, is one of the world’s largest polluters and recently made recent headlines when it withdrew from the Paris Agreement negotiated at the 2015 United Nations Climate Change Conference (COP21).
Putting into place effective measures to curtail climate change while creating sustainable societies requires international cooperation. The series of extreme weather events in the US in 2017 are only some the most recent disasters to remind us of climate change’s threat to our economy, our society, and our individual daily lives.
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Integrated assessment models generate climate change mitigation scenarios consistent with global temperature targets. To limit warming to 2 °C, cost-effective mitigation pathways rely on extensive deployments of CO2 removal (CDR) technologies, including multi-gigatonne yearly CDR from the atmosphere through bioenergy with carbon capture and storage (BECCS) and afforestation/reforestation. While these assumed CDR deployments keep ambitious temperature targets in reach, the associated rates of land-use transformation have not been evaluated. Here, we view implied integrated-assessment-model land-use conversion rates within a historical context. In scenarios with a likely chance of limiting warming to 2 °C in 2100, the rate of energy cropland expansion supporting BECCS proceeds at a median rate of 8.8 Mha yr−1 and 8.4% yr−1. This rate exceeds—by more than threefold—the observed expansion of soybean, the most rapidly expanding commodity crop. In some cases, mitigation scenarios include abrupt reversal of deforestation, paired with massive afforestation/reforestation. Historical land-use transformation rates do not represent an upper bound for future transformation rates. However, their stark contrast with modelled BECCS deployment rates implies challenges to explore in harnessing—or presuming the ready availability of—large-scale biomass-based CDR in the decades ahead. Reducing BECCS deployment to remain within these historical expansion rates would mean either the 2 °C target is missed or additional mitigation would need to occur elsewhere.
Roz Naylor, Director of the Center on Food Security and the Environment talks how technology will help meet the growing demand for food and water in the developing world and why tech companies should invest in Africa.
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Roz Naylor and Russ Altman talk the future of food security. | Stanford Radio
The availability of climate model experiments under three alternative scenarios stabilizing at warming targets inspired by the COP21 agreements (a 1.5 ºC not exceed, a 1.5 ºC with overshoot and a 2.0ºC) makes it possible to assess future expected changes in global yields for two staple crops, wheat and maize. In this study an empirical model of the relation between crop yield anomalies and temperature and precipitation changes, with or without the inclusion of CO2 fertilization effects, is used to produce ensembles of time series of yield outcomes on a yearly basis over the course of the 21st century, for each scenario. The 21st century is divided into 10 year windows starting from 2020, within which the statistical significance and the magnitude of the differences in yield changes between pairs of scenarios are assessed, thus evaluating if, and when, benefits of mitigations appear, and how substantial they are. Additionally, a metric of extreme heat tailored to the individual crops (number of days during the growing season above a crop-specific threshold) is used to measure exposure to harmful temperatures under the different scenarios. If CO2 effects are not included, statistically significant differences in yields of both crops appear as early as the 2030s but the magnitude of the differences remains below 3% of the historical baseline in all cases until the second part of the century. In the later decades of the 21st century, differences remain small and eventually stop being statistically significant between the two scenarios stabilizing at 1.5 ºC, while differences between these two lower scenarios and the 2.0ºC scenario grow to about 4%. The inclusion of CO2 effects erases all significant benefits of mitigation for wheat, while the significance of differences is maintained for maize yields between the higher and the two lower scenarios, albeit with smaller benefits in magnitude. Changes in extremes are significant within each of the scenarios but the differences between any pair of them, even by the end of the century are only on the order of a few days per growing season, and these small changes appear limited to a few localized areas of the growing regions. These results seem to suggest that for globally averaged yields of these two grains the lower targets put forward by the Paris agreement does not change substantially the expected impacts on yields that are caused by warming temperatures under the pre-existing 2.0ºC target.
Elevated atmospheric CO2 concentrations ([CO2]) are expected to increase C3 crop yield through the CO2 fertilization effect (CFE) by stimulating photosynthesis and by reducing stomatal conductance and transpiration. The latter effect is widely believed to lead to greater benefits in dry rather than wet conditions, although some recent experimental evidence challenges this view. Here we used a process-based crop model, the Agricultural Production Systems sIMulator (APSIM), to quantify the contemporary and future CFE on soybean in one of its primary production area of the US Midwest. APSIM accurately reproduced experimental data from the Soybean Free-Air CO2 Enrichment site showing that the CFE declined with increasing drought stress. This resulted from greater radiation use efficiency (RUE) and above-ground biomass production at elevated [CO2] that outpaced gains in transpiration efficiency (TE). Using an ensemble of eight climate model projections, we found that drought frequency in the US Midwest is projected to increase from once every 5 years currently to once every other year by 2050. In addition to directly driving yield loss, greater drought also significantly limited the benefit from rising [CO2]. This study provides a link between localized experiments and regional-scale modeling to highlight that increased drought frequency and severity pose a formidable challenge to maintaining soybean yield progress that is not offset by rising [CO2] as previously anticipated. Evaluating the relative sensitivity of RUE and TE to elevated [CO2] will be an important target for future modeling and experimental studies of climate change impacts and adaptation in C3 crops.
Abstract: Effective climate risk management requires robust quantification of the probability of different kinds of hazards, such as heat waves, droughts, floods, and severe storms. As a result, there has been increasing interest in the extent to which historical global warming has influenced the occurrence and severity of individual extreme climate events. However, although trends in the extremes of the seasonal- and daily-scale distributions of climate records have been analyzed for many years, quantifying the contribution of observed global warming to individual events that are unprecedented in the observed record presents a particular scientific challenge. I will describe a framework for leveraging observations and large climate model ensembles to quantify the influence of observed global warming on the probability of unprecedented extreme events. This approach is grounded on three tenets: (1) Focus on understanding the physical causes of the individual event; (2) Use formal uncertainty quantification to test the probability of those physical conditions occurring in the current climate; and (3) Use formal hypothesis testing to compare the probability of those physical conditions occurring in the current climate and a climate without human influence. My group has applied our analysis to a number of different climate variables from a number of individual events, including temperature, precipitation, soil moisture, and atmospheric circulation patterns. Together, this work has shown that global warming can influence the risk of extreme events that are unprecedented in historical experience, particularly by altering the probability of the physical conditions that are responsible for the event. In addition, given the widespread public interest in “real time” attribution, the prospects for operational attribution analysis will also be discussed.
About the Speaker: Noah Diffenbaugh is a Professor and Kimmelman Family Senior Fellow at Stanford University. He studies the climate system, including impacts on agriculture, water resources, and human health. He is currently Editor-in-Chief of Geophysical Research Letters. He has served as an IPCC Lead Author, and has provided scientific expertise to the White House, the Governor of California, and U.S. Congressional offices. Recognitions include the Holton Award from the American Geophysical Union and a CAREER award from the National Science Foundation.
Encina Hall, 2nd floor
Noah S. Diffenbaugh
Professor, School of Earth, Energy and Environmental Sciences
Stanford University
In a shack that now sits below sea level, a mother in Bangladesh struggles to grow vegetables in soil inundated by salt water. In Malawi, a toddler joins thousands of other children perishing from drought-induced malnutrition. And in China, more than one million people died from air pollution in 2012 alone.
Around the world, climate change is already having an effect on human health.
In a recent paper, Katherine Burke and Michele Barry from the Stanford Center for Innovation in Global Health, along with former Wellesley College President Diana Walsh, described climate change as “the ultimate global health crisis.” They offered recommendations to the new United States president to address the urgently arising health risks associated with climate change.
Bangladeshi children make their way through flood waters.
The authors, along with Stanford researchers Marshall Burke, Eran Bendavid and Amy Pickering who also study climate change, are concerned by how little has been done to mitigate its effects on health.
There is still time to ease — though not eliminate — the worst effects on health, but as the average global temperature continues to creep upward, time appears to be running short.
“I think we are at a critical point right now in terms of mitigating the effects of climate change on health,” said Amy Pickering, a research engineer at the Woods Institute for the Environment. “And I don’t think that’s a priority of the new administration at all.”
Health effects of climate change
Even in countries like the United States that are well-equipped to adapt to climate change, health impacts will be significant.
“Extremes of temperature have a very observable direct effect,” said Eran Bendavid, an assistant professor of medicine and Stanford Health Policy core faculty member.
“We see mortality rates increase when temperatures are very low, and especially when they are very high.”
Bendavid also has seen air pollutants cause respiratory problems in people from Beijing to Los Angeles to villages in Sub-Saharan Africa.
“Hotter temperatures make it such that particulate matter and dust and pollutants stick around longer,” he said.
In addition to respiratory issues, air pollution can have long-term cognitive effects. A study in Chile found that children who are exposed to high amounts of air pollution in utero score lower on math tests by the fourth grade.
“I think we’re only starting to understand the true costs of dirty air,” said Marshall Burke. “Even short-term exposure to low levels can have life-long effects.”
Low-income countries like Bangladesh already suffer widespread, direct health effects from rising sea levels. Salt water flooding has crept through homes and crops, threatening food sources and drinking water for millions of people.
“I think that flooding is one of the most pressing issues in low-income and densely populated countries,” said Pickering. “There’s no infrastructure there to handle it.”
Standing water left over from flooding is also a breeding ground for diseases like cholera, diarrhea and mosquito-borne illnesses, all of which are likely to become more prevalent as the planet warms.
On the flip side, many regions of Sub-Saharan Africa — where clean water is already hard to access — are likely to experience severe droughts. The United Nations warned last year that more than 36 million people across southern and eastern Africa face hunger due to drought and record-high temperatures.
Residents may have to walk farther to find water, and local sources could become contaminated more easily. Pickering fears that losing access to nearby, clean water will make maintaining proper hygiene and growing nutritious foods a challenge.
Climate change will affect health in all sectors of society.
All of these effects and more can also damage mental health, said Katherine Burke and her colleagues in their paper. The aftermath of extreme weather events and the hardships of living in long-term drought or flood can cause anxiety, depression, grief and trauma.
Climate change will affect health in every sector of society, but as Katherine Burke and her colleagues said, “….climate disruption is inflicting the greatest suffering on those least responsible for causing it, least equipped to adapt, least able to resist the powerful forces of the status quo.
“If we fail to act now,” they said, “the survival of our species may hang in the balance.”
What can the new administration do to ease health effects?
If the Paris Agreement’s emissions standards are met, scientists predict that the world’s temperature will increase about 2.7 degrees Celsius – still significant but less hazardous than the 4-degree increase projected from current emissions.
The United States plays a critical role in the Paris Agreement. Apart from the significance of cutting its own emissions, failing to live up to its end of the bargain — as the Trump administration has suggested — could have a significant impact on the morale of the other countries involved.
“The reason that Paris is going to work is because we’re in this together,” said Marshall Burke. “If you don’t meet your target, you’re going to be publicly shamed.”
The Trump administration has also discussed repealing the Clean Power Plan, Obama-era legislation to decrease the use of coal, which has been shown to contribute to respiratory disease.
“Withdrawing from either of those will likely have negative short- and long-run health impacts, both in the U.S. and abroad,” said Marshall Burke.
Scott Pruitt, who was confirmed today as the head of the Environmental Protection Agency (EPA), is expected to carry out Trump’s promise to dismantle environment regulations.
Despite the Trump administration’s apparent doubts about climate change, a few prominent Republicans do support addressing its effects.
Secretary of State Rex Tillerson, the former chairman and CEO of Exxon Mobile, supports a carbon tax, which would create a financial incentive to turn to renewable energy sources. He also has expressed support for the Paris Agreement. It is possible that as secretary of state, Tillerson could help maintain U.S. obligations from the Paris Agreement, though it is far from certain whether he would choose to do so or how Trump would react.
More promising is a recent proposal from the Climate Leadership Council. Authored by eight leading Republicans — including two former secretaries of state, two former secretaries of the treasury and Rob Walton, Walmart’s former chairman of the board — the plan seeks to reduce emissions considerably through a carbon dividends plan.
Already an issue, malnutrition will increase with droughts in Sub-Saharan Africa.
Their proposal would gradually increase taxes on carbon emissions but would return the proceeds directly to the American people. Americans would receive a regular check with their portion of the proceeds, similar to receiving a social security check. According to the authors, 70 percent of Americans would come out ahead financially, keeping the tax from being a burden on low- and middle-income Americans while still incentivizing lower emissions.
“A tax on carbon is exactly what we need to provide the right incentives and induce the sort of technological and infrastructure change needed to reduce long-term emissions,” said Marshall Burke.
Pickering added, “This policy is a ray of hope for meaningful action on climate.”
It remains to be seen whether the new administration and congress would consider such a program.
What can academics do to help?
Meanwhile, academics can promote health by researching the effects of climate change and finding ways to adapt to them.
“I think it’s fascinating that there’s just so little data right now on how climate change is going to impact health,” said Pickering.
Studying the effects of warming on the world challenges traditional methods of research.
“You can’t create any sort of experiment,” said Bendavid. “There’s only one climate and one planet.”
The scholars agree that interdisciplinary study is a critical part of adapting to climate change and that more research is needed.
“If ever there was an issue worthy of a leader’s best effort, this is the moment, this is the issue,” said Katherine Burke and her colleagues. “Time is short, but it may not be too late to make all the difference.”
Percentage gain in GDP per capita in 2100 from achieving 1.5 degrees Celsius global warming instead of 2 degrees.
Bangladeshi children make their way through flood waters.
Climate change will affect health in all sectors of society.
Already an issue, malnutrition will increase with droughts in Sub-Saharan Africa.
