The science behind decarbonization
A collection of research and insights from Stanford experts who are revealing the stakes of emission cuts, enabling better carbon accounting, predicting the consequences of future emission pathways and mapping out viable solutions.
By the start of a virtual climate summit on Earth Day, April 22, the Biden administration is expected to outline a new target for cutting U.S. greenhouse gas emissions this decade.
Already, climate change has hurt farm productivity, caused tens of billions of dollars in flood damages in the U.S. alone, and increased the the risk of longer, more dangerous wildfire seasons in California. The goal of deep emission cuts is to slow the world’s advancement toward a dangerous temperature threshold beyond which climate impacts are likely to become more severe and widespread, including droughts, extreme heatwaves and floods.
In the 2015 Paris Climate Agreement, nearly 200 nations committed to holding this century’s average temperature to well below 2°C and to “pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change.”
Current commitments fall short of that aspirational goal. A 2018 paper led by Stanford climate scientist Noah Diffenbaugh found the gap could considerably increase the likelihood of extreme weather. Other research suggests failing to meet the accord’s climate mitigation goals could cost the global economy tens of trillions of dollars. The lead study author, environmental economist Marshall Burke, has said, “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."
The current U.S. emission pledge, made under former President Barack Obama, targets cuts of 26 to 28 percent below 2005 levels by 2025. In November 2021, countries participating in major UN climate talks (COP26) in Glasgow, Scotland, will be expected to announce new, more ambitious plans for slashing their emissions over the next decade.
More than 300 businesses and investors have urged the Biden administration to commit to reducing greenhouse gas emissions to at least 50 percent below 2005 levels by 2030, “in pursuit of reaching net-zero emissions by 2050.” European lawmakers, trade unions, businesses and environmental groups have also called for the U.S. – the world’s largest historical carbon emitter – to cut emissions at least 50 percent below 2005 levels this decade.
Halving the nation’s emissions will require significant changes. This collection covers how scientists are evaluating the stakes of emission cuts, enabling better carbon accounting, predicting the consequences of future emission pathways and mapping out viable solutions.
Scroll down for research news and insights spanning emission targets; the role of renewable energy and grid storage; prospects for adaptation and a more equitable recovery; the future of fossil fuels and carbon capture; the promise and limits of natural climate solutions such as reforestation – and more.
Last updated: April 26, 2021
“The really big increases in record-setting event probability are reduced if the world achieves the aspirational targets rather than the actual commitments,” said Stanford professor Noah Diffenbaugh. “At the same time, even if those aspirational targets are reached, we still will be living in a climate that has substantially greater probability of unprecedented events than the one we’re in now.”
Among the dozens of countries that reduced their emissions 2016-2019, carbon dioxide emissions fell at roughly one tenth the rate needed worldwide to hold global warming well below 2°C relative to preindustrial levels, a new study finds.
An international group of experts, including Stanford Earth system scientist Rob Jackson, has published a roadmap of the most viable solutions for slashing greenhouse gas emissions globally by 2030.
Researchers propose three separate ways to avoid blackouts if the world transitions all its energy to electricity or direct heat and provides the energy with 100 percent wind, water and sunlight. The solutions reduce energy requirements, health damage and climate damage.
As power grids move away from fossil fuels, companies seeking to cut out carbon emissions will have to go beyond commitments to renewable energy.
Storing energy produced by wind or solar for later use has a challenge competing with existing natural gas-fired generation units. But batteries designed for the job could ease the way.
Electricity has a clear path to decarbonization, Stanford Law School lecturer Danny Cullenward tells NPR. "The technologies that cut the emissions are things we have and we know how to work with. That's installing solar plants. That's installing wind plants. That's putting in battery energy storage systems. And we have the right policies and tools to get it done."
"We need to move as quickly as we can with technologies that are ready to go, like wind and solar power, and continue to develop other critical components of a deeply decarbonized energy system like large-scale weekly to seasonal energy storage," said energy resources engineering professor Sally Benson.
Scientists have estimated the emissions intensity of carbon dioxide and other air pollutants from a major electricity distributor and highlighted key consequences – essential information for policymakers shaping decisions to reduce electricity system emissions.
“I have grave misgivings about gigaton-scale natural solutions,” or forestry offsets, said Stanford Earth system science professor Rob Jackson. “And gigaton-scale is the only thing that matters when we’re talking about the coal and oil and natural gas industries.”
Research suggests large reductions in economic productivity can persist many years after a storm, yet few people connect foregone earnings today to a hurricane long past, economist Solomon Hsiang said in a discussion moderated by Stanford's Marshall Burke. The role of the policymaker, Hsiang said, could be fostering innovation that will bring the cost of adaptation technology down, or helping populations feel some of the more subtle impacts as something that will be more salient.
"We got to where we are now on climate through a history of white supremacy, extraction, exploitation," Alicia Seiger, managing director of the Sustainable Finance Initiative at Stanford's Precourt Institute for Energy tells Climate One. "That requires a path forward built on new systems with new representation, and that the solutions to climate expand far beyond simple carbon math."
"I think one thing that history can really offer to fixing the climate problem is to say look, we have known about this climate issue for a very long time for many, many decades. How is it that we have made such unsatisfactory progress in dealing with it," said Benjamin Franta, a Stanford PhD student researching the history of science.
Reducing greenhouse gas emissions from food systems will be vital to reaching climate goals – and it will require coordinated action across sectors and between national governments, according to new research coauthored by Inês Azevedo, associate professor of energy resources engineering.
Nitrous oxide, also known as “laughing gas,” is the most important greenhouse gas after methane and carbon dioxide and the biggest human-related threat to the ozone layer. Stanford scientist Rob Jackson explains why emissions of the gas are rising faster than expected and what it will take to reverse the trend.
A new study finds emissions from deforestation, conversion of wild landscapes to agriculture, and other changes in land use worldwide contributed 25 percent of all human-caused emissions between 2001 and 2017. Expanding agricultural production in Latin America, Southeast Asia and sub-Saharan Africa has propelled the global increase.
"We’re unlikely to be able to keep global warming within 1.5 degrees Celsius without cutting methane emissions ... also finding ways to neutralize methane already in the atmosphere," write Rob Jackson of Stanford and Daphne Wysham of the NGO Methane Action in an op-ed.
Emissions of methane, a potent greenhouse gas, from water heaters are higher than previously estimated, especially for a new type of heater growing in popularity, a new Stanford study finds. But simple fixes exist.
HFCs are all around us, and they're hundreds to thousands of times more potent greenhouse gases than carbon dioxide.
With transportation belching out 28 percent of US carbon emissions, fuel economy will have to be a big part of the new administration’s climate plan. “The government needs to create a regulatory market through policies and subsidies,” Stanford environmental law professor Deborah Sivas tells Popular Science. “In the end, that’s what’s going to move the ball for industry – just like how these car companies got on board in California.”
"Almost $50 billion of stimulus funding after the 2008 recession helped transform wind and solar power and energy conservation. We’re still reaping the benefits today from green power, historically cheap wind and solar contracts and a clean-energy industry that employs three million Americans. We have the same chance to reshape transportation now," said Stanford professor Rob Jackson.
Researchers examined the most beneficial vehicle fuel technology for transportation in the US and the trade-off between decarbonization and air pollution mitigation. The results show electric vehicle use must accompany clean energy grids to mitigate both climate change and air pollution.
A new analysis looks at what it would take for oil companies to start pumping millions of tons of carbon dioxide into their wells to boost crude production – and what it would mean for the climate.
With recent tax credits and other policies, removing carbon dioxide from the atmosphere and storing it underground is not only possible but profitable for U.S. biofuel refineries. "“There’s really no scenario that meets the world’s climate goals without negative emissions,” said Katharine Mach.
"Increasingly carbon removal is being taken seriously," said Dan Reicher, a senior research scholar at Stanford who was on the energy transition team for former President Obama and helped put together the 2009 stimulus package. "It's become a mainstream option, and now the question is, 'Can it really be proven to work at scale and cost effectively?' That's the open question."
Once considered a distraction, scientists now say using technology—and nature – to remove carbon dioxide from the atmosphere is not only possible: It’s a must.
New research suggests managing and disposing of high salinity brines – a by-product of efficient underground carbon sequestration – will impose significant energy and emissions penalties. The work quantifies these penalties for different management scenarios and provides a framework for making the approach more energy efficient.
“There is a lot of reliance on carbon capture in theoretical modeling, and by focusing on that as even a possibility, that diverts resources away from real solutions,” said Stanford engineering professor Mark Z. Jacobson. “It gives people hope that you can keep fossil fuel power plants alive. It delays action. In fact, carbon capture and direct air capture are always opportunity costs.”