Rising atmospheric carbon dioxide concentrations are anticipated to decrease the zinc and iron concentrations of crops. The associated disease burden and optimal mitigation strategies remain unknown. We sought to understand where and to what extent increasing carbon dioxide concentrations may increase the global burden of nutritional deficiencies through changes in crop nutrient concentrations, and the effects of potential mitigation strategies.
The rising level of carbon dioxide in the atmosphere means that crops are becoming less nutritious, and that change could lead to higher rates of malnutrition that predispose people to various diseases.
That conclusion comes from an analysis published Tuesday in the journal PLOS Medicine, which also examined how the risk could be alleviated. In the end, cutting emissions, and not public health initiatives, may be the best response, according to the paper's authors.
Research has already shown that crops like wheat and rice produce lower levels of essential nutrients when exposed to higher levels of carbon dioxide, thanks to experiments that artificially increased CO2 concentrations in agricultural fields. While plants grew bigger, they also had lower concentrations of minerals like iron and zinc.
Poor air quality is thought to be an important mortality risk factor globally1,2,3, but there is little direct evidence from the developing world on how mortality risk varies with changing exposure to ambient particulate matter. Current global estimates apply exposure–response relationships that have been derived mostly from wealthy, mid-latitude countries to spatial population data4, and these estimates remain unvalidated across large portions of the globe. Here we combine household survey-based information on the location and timing of nearly 1 million births across sub-Saharan Africa with satellite-based estimates5 of exposure to ambient respirable particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) to estimate the impact of air quality on mortality rates among infants in Africa. We find that a 10 μg m−3 increase in PM2.5 concentration is associated with a 9% (95% confidence interval, 4–14%) rise in infant mortality across the dataset. This effect has not declined over the last 15 years and does not diminish with higher levels of household wealth. Our estimates suggest that PM2.5 concentrations above minimum exposure levels were responsible for 22% (95% confidence interval, 9–35%) of infant deaths in our 30 study countries and led to 449,000 (95% confidence interval, 194,000–709,000) additional deaths of infants in 2015, an estimate that is more than three times higher than existing estimates that attribute death of infants to poor air quality for these countries2,6. Upward revision of disease-burden estimates in the studied countries in Africa alone would result in a doubling of current estimates of global deaths of infants that are associated with air pollution, and modest reductions in African PM2.5 exposures are predicted to have health benefits to infants that are larger than most known health interventions.
Satellite measurements of air quality across sub-Saharan Africa revealed small improvements in air quality could be one of the most effective interventions to curb infant mortality rates.
In 2015, exposure to particulate matter in sub-Saharan Africa led to 400,000 otherwise preventable infant deaths, according to a new Stanford study. The research, published this week in Nature, finds that even modest improvements in air quality could lead to substantial reductions in infant mortality in developing countries.
“Many wealthy countries have recently used legislation to clean up their air,” said Marshall Burke, study co-author and assistant professor of Earth system science in the School of Earth, Energy & Environmental Sciences at Stanford. “We find that if countries in Africa could achieve reductions in particulate matter exposure similar to wealthy countries, the benefits to infant health could be larger than nearly all currently used health interventions, such as vaccinations or food and water supplements.”
Led by Sam Heft-Neal, a research scholar at Stanford’s Center on Food Security and the Environment, the research team combined 15 years of survey data on nearly 1 million births across sub-Saharan Africa with satellite-based measurements of particulate matter, an important contributor to poor air quality. The mixture of microscopic particles in the air can cause serious health effects when inhaled.
“We know that breathing dirty air is bad for your health,” said Heft-Neal. “But in developing countries in particular, we don’t yet know how big a threat poor air quality is relative to other common health risks like poor nutrition and infectious disease.”
Understanding the impact of poor air quality in developing countries has traditionally been difficult, as most do not have on-the-ground pollution monitors or vital registration data recording birth outcomes. To overcome these constraints, the research team compiled data from 65 household surveys across 30 sub-Saharan African countries spanning from 2001 to 2015. Using new satellite-based measures of ambient particulate matter, they then compared the particulate matter each infant was exposed to while in utero and after birth. From this, they could relate exposure to particulate matter with health outcomes.
“The results were sobering,” said Burke. “We find that mortality rates are substantially higher for infants exposed to higher levels of particulate matter.”
The researchers found that high particulate matter concentrations were responsible for 22 percent of infant deaths from 2001 to 2015. They also found that this number has not decreased over the past 15 years and remains unchanged even in wealthier households.
The group’s estimate of the effect of particulate matter exposure on mortality is about three times larger than existing estimates, suggesting poor air quality is an even bigger problem than currently believed. The main explanation for these larger estimates, according to the study’s authors, is that exposure to particulate matter can lead to a range of negative health effects, including lower birth weight and impaired growth in the first year of life, beyond those typically considered in health analyses.
One of the study’s most important implications is that relatively small decreases in particulate matter concentrations could result in major reductions in mortality.
The researchers conclude that finding cost-effective ways to reduce particulate matter exposure should be a research and policy priority. “We now have a better sense of the immense benefits of air quality improvements for infant health,” said Heft-Neal. “Next we need to establish how these improvements can be achieved.”
Climate-induced shocks in grain production are a major contributor to global market volatility, which creates uncertainty for cereal farmers and agribusiness and reduces food access for poor consumers when production falls and prices spike. Our study, by combining empirical models of maize production with future warming scenarios, shows that in a warmer climate, maize yields will decrease and become more variable. Because just a few countries dominate global maize production and trade, simultaneous production shocks in these countries can have tremendous impacts on global markets. We show that such synchronous shocks are rare now but will become much more likely if the climate continues to warm. Our results underscore the need for continued investments in breeding for heat tolerance.
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
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.
Percentage gain in GDP per capita in 2100 from achieving 1.5 degrees Celsius global warming instead of 2 degrees.