Dear Sara,

My brother says that some economists have taken the view that 3 degrees Celsius is the most reasonable target for warming, and that limiting warming to 1.5 degrees Celsius would just make the world poorer.

Many people now have this view — i.e., that keeping the temperature to 1.5 degrees Celsius is just too expensive.

How can I debate this?

Mark in Randolph, New Jersey

Hi Mark,

Try starting with the values that you and your brother hold in common. From your letter, it sounds as though you both believe that poverty is a major problem. Rather than trying to debate him, surprise him by telling him that you agree: It’s important to protect the climate and to reduce global poverty.

Ask your brother questions. What are his specific concerns about the costs of addressing climate change? What does he imagine will happen if societies spend a lot of money trying to slow the Earth’s warming? Listen to his answers. (For more on the value of listening, see this essay by Karin Kirk, a Yale Climate Connections contributor.)

How will global warming affect the world’s poor?

After you’ve listened — seriously, you can’t skip this step — you might share your own concerns about the costs of a warming climate.

If you’re interested in learning more about that topic, a place to start is the 2020 book “Our Final Warning: Six Degrees of Climate Emergency,” by British journalist Mark Lynas. Lynas has scoured the scientific literature on climate change to paint a picture of the conditions the world can expect to face as it warms. The book is organized by degrees: The first chapter describes the consequences of warming the world by one degree Celsius, the second describes the likely outcomes of warming by two degrees, and so on. (For American readers, a change of one degree Celsius is 1.8 degrees Fahrenheit, 2 degrees Celsius is 3.6 degrees Fahrenheit, and 3 degrees Celsius is 5.4 degrees Fahrenheit.)

Notably, we’ve already warmed the Earth by a little more than one degree Celsius since 1880, so Lynas’s first chapter describes the recent past and present day. At one degree of warming, we’re already seeing worrisome signs that climate change is harming people living in poverty. Take 2017’s Hurricane Harvey, which dumped feet of rain on Texas to devastating, long-lasting effect for low-income people. Scientists have found that the storm’s rains were made worse by human-caused climate change.

In 2019, before the COVID-19 pandemic shook the world’s economy, the UN warned that climate change could reverse recent gains in addressing global poverty: “Extreme weather conditions, more frequent and severe natural disasters and the collapse of ecosystems are causing increased food insecurity and are … worsening people’s safety and health, forcing many communities to suffer from poverty, displacement and widening inequalities.”

At two degrees Celsius of warming, Lynas reports, the dangers from flooding and severe storms are likely to grow. That much warming is likely to cause enough additional ice melt in the Arctic and Antarctic to lead, over centuries, to a rise of more than 16 feet in sea levels. That would inundate many of the world’s megacities and low-lying countries, such as Bangladesh.

Meanwhile, an estimated 410 million additional people could be exposed to severe drought conditions around the world. One two-degree projection, Lynas writes, “condemns virtually the entire African continent, Australia, the Middle East, western India and China, south-east Asia, most of South America and the western half of North America to increased drought duration and frequency, adding up to a 20% increase in drought overall.”

Compared to a world in which no warming has taken place, the two-degree warmer world is expected to see a reduction in global food availability of 99 calories per person a day, with more than 500,000 deaths by 2050 related to malnutrition.

At three degrees Celsius of warming, the scientific literature shifts from grim to bleak. Lynas reports that the potential effects include:

  • Sea-level rise by 2100 inundating land area occupied by 50 million people — with some estimates projecting that hundreds of millions will be displaced
  • Fifty million people experiencing temperatures too hot for survival, with those living in poor nations, such as North and South Sudan, Burkina Faso, Mauritania, and Bolivia, in the most danger. In South Asia, hundreds of millions of people could suffer from heat waves “considered extremely dangerous for most humans” — conditions so hot that agricultural work, road repair, and other outdoor labor would temporarily halt and unsheltered livestock would die.
  • Arid lands expanding to cover half the world’s land area
  • One billion people experiencing threats to their water supplies, with those in poor countries most at risk
  • Global food production falling as conditions no longer allow subsistence or smallholder farming across much of Africa and South Asia.

Mark, it is true that some economists have argued that the costs of limiting global warming are high. But as my colleague Dana Nuccitelli has reported, economic models have a history of underestimating the true costs of climate change. And as you can see from the list above, the potential consequences of letting the world warm by three degrees Celsius are enormous.

As Lynas writes, “Human societies can aim to survive the two-degree world in some semblance of their current condition. Another degree, however, will stress our civilisation towards the point of collapse. If we choose to enter the three-degree world — and to do so still remains a choice — we must do so with our eyes open.”

What do representatives of the world’s poorest countries say about global warming?

You can also encourage your brother to seek sources of information beyond the discipline of economics. For instance, he might consider learning more about what people living in low-income countries are saying and doing about climate change.

Keeping in mind that people living in poor countries are not a monolith, let’s walk through a few examples.

In November 2019, Bangladesh’s parliament unanimously passed a motion declaring a “planetary emergency.” Citing his country’s vulnerability to climate change, MP Saber Hossain Chowdhury urged the global community to act swiftly to limit warming to 1.5 degrees Celsius.

Two decades of civil war have left Somalia one of the world’s most fragile and poorest countries. Yet leaders there are working to reduce the country’s emissions of heat-trapping gases by 30% by 2030.

Burundi, a country of 11.5 million people in East Africa, has one of the lowest per-capita GDPs in the world. In a French-language speech delivered at the UN Climate Change Conference in Madrid in 2019, Ndorimana Emmanuel, Burundi’s minister of the environment, agriculture, and livestock, described life on this planet under climate change as “a perpetual struggle.” He added that extreme droughts and floods are already harming agriculture in Burundi and pressed rich nations to provide climate-related aid to his country.

Notably, 190 of the world’s 197 countries have formally endorsed the Paris agreement, in which they committed to cut emissions in order to limit warming to 2 degrees Celsius above the pre-industrial average and to “pursue efforts” to limit warming to 1.5 degrees Celsius. Bangladesh, Somalia, Burundi, and many of the world’s other poorest countries are among the signatories.

And there’s this August 2020 statement from Sonam Wangdi, the chair of the Least Developed Countries Group, which represents the 47 poorest countries in climate negotiations: “Action on climate change must not be delayed,” Wangdi said. “It is critical that all governments, and particularly those governments of wealthy nations currently making stimulus plans to build their economies back ensure that spending is consistent with steep emissions reductions and aligned with 1.5 degree Celsius pathways and the goals of the Paris agreement.”

In other words, far from begging the world to let the Earth warm by 3 degrees Celsius, scientists and representatives of poor countries are framing climate action as crucial to their survival. We should listen.

– Sara

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Tom Toro is a cartoonist and writer who has published over 200 cartoons in The New Yorker since 2010.

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Sara Peach is the editor-in-chief of Yale Climate Connections. She is an environmental journalist whose work has appeared in National Geographic, Scientific American, Environmental Health News, Grist,...