The Super Tuesday Survivors

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Super Tuesday has narrowed the Democratic presidential contest to a two-man race between Senator Bernie Sanders and former Vice President Joe Biden. Here are the key differences between those candidates’ plans to tackle global warming.

The targets: Mr. Biden’s plan calls for 100 percent carbon-free energy (essentially renewables or nuclear power) and net-zero emissions (eliminating as much planet-warming carbon dioxide as is being emitted) by 2050. Senator Sanders’s plan envisions the electricity and transportation sectors running solely on renewable power no later than 2030, and an end to the use of fossil fuels no later than 2050.

How to get there: Both Mr. Biden and Mr. Sanders focus heavily on new regulations that would not require congressional approval, as well as spending federal dollars to incentivize the deployment of clean energy across the economy. Neither calls for a tax on carbon emissions. The core of Mr. Sanders’ plan for the power sector involves convincing Congress to authorize and allocate about $2 trillion for a government-run effort to manage and distribute renewable energy.

Costs: Mr. Biden says his plan would cost $1.7 trillion. Mr. Sanders has placed the price of his at $16.3 trillion.

How to pay: Both candidates have outlined various measures that call for greater taxes and unspecified new fees on corporations as well as eliminating fossil fuel subsidies.

Jobs: Extrapolating how many jobs any climate plan will create is a tricky business. But based on Mr. Biden’s own projections, his plan would generate 10 million jobs. Mr. Sanders says his would create 20 million.

Technology: Mr. Sanders has called geoengineering (the deliberate manipulation of the climate to counteract the effects of global warming), nuclear power and carbon capture “false solutions.” His plan would halt construction of new nuclear plants and end license renewals for existing ones until a solution for nuclear waste is found. Mr. Biden’s plan contends that addressing climate change must consider “all low- and zero-carbon technologies” including nuclear and carbon capture. His plan does not mention geoengineering, which includes ideas like space mirrors to reflect away sunlight and ocean fertilization.

Natural Gas: Mr. Sanders has called for a nationwide ban on fracking and phasing out natural gas plants. Mr. Biden’s blueprint does not explicitly mention either but he has said on the campaign trail that he favors enhanced regulations on natural gas extraction and fracking, though not a nationwide ban.

Air pollution is killing more people than war, malaria or cigarettes. That’s the conclusion of a scientific paper published this week that quantified the causes of premature deaths from various sources.

It found that, in 2015, the one year investigated, 8.8 million excess deaths could be attributed to air pollution, which is far greater than any other cause of premature mortality. Smoking was nearly as bad, killing 7.2 million that year, the study found. Vector-borne diseases like malaria caused 600,000 deaths. Violence, including wars, claimed 530,000 lives.

(As for viral diseases, a separate study in 2018 found that the seasonal flu virus kills between 291,000 and 646,000 people a year, a great many more than the death toll of around 3,200 from the coronavirus so far this year.)

One of the lead researchers, Thomas Münzel, a cardiologist at the Johannes Gutenberg University Medical Center in Mainz, Germany, said in a statement, “We believe our results show there is an ‘air pollution pandemic.’”

A 2018 study known as the Global Exposure Mortality Model, which used similar data from 16 countries, came up with a comparable estimate: 8.9 million deaths from exposure to fine particulate matter. These estimates are far larger than earlier findings using other risk models.

The study, published in the journal Cardiovascular Research, investigated what effect air pollution has on things like cardiovascular disease, lung cancer, respiratory tract infections and chronic obstructive pulmonary disease. Among those, they found that cardiovascular disease claimed the most lives. The researchers pressed health professionals, especially cardiologists, to pay more attention to air pollution impacts.

Their calculations suggested that air pollution shortened life expectancy by nearly three years. Most of the deaths were among people over 60.

East Asia and South Asia were the worst-hit parts of the world.