Posted on 20 October 2021 by dana1981

This is a re-post from Yale Climate Connections

It’s the moral quandary of human-caused climate change: People least responsible for the problem will bear the brunt of its harmful consequences. As a substantial body of scientific research has established, this reality is true of developing countries. They generally are located in already-hot regions near the equator and lack needed financial resources to adapt to the changing climate.

As a new study in the journal Science illustrates, this conundrum applies also to younger generations being born into a carbon-intensive society and a world undergoing rapid climate change. Children born today will experience far more extreme weather impacts over their lifetimes than their grandparents, particularly those children born in vulnerable developing countries.

This issue of intergenerational climate impacts is also a critical consideration for economics and policy in the present day. Decisions about whether governments should invest money in climate solutions today, or save those funds to accrue interest in the future, are based on subjective choices and values. Would societies prefer that future generations inherit less economic debt but an increasingly destabilized climate with worse extreme weather impacts? The new Science study provides important context with which to weigh those choices.

Severe changes in extreme heat waves

More frequent and intense heat waves are the most direct consequence of global warming. Burning fossil fuels releases carbon that combines with oxygen in the air to form the greenhouse gas carbon dioxide, which traps more heat and thus raises Earth’s temperatures.

The latest report from the Intergovernmental Panel on Climate Change indicates that what was a 1-in-50-year extreme heat event in the late-1800s now happens five times more often – once per decade. As temperatures approach the Paris Climate Agreement target of 1.5 to 2 degrees Celsius (2.7 to 3.6 degrees Fahrenheit) above pre-industrial levels, that frequency will again double: The same extreme heat wave will occur once every five years.

The new Science study arrives at the same general conclusion but frames these impacts in a novel way, in terms of how frequently a cohort generation will experience the same level of extreme weather during their lifetimes. For example, what was a once-in-a-lifetime heat wave for a person born in the 1800s (a level of extreme heat happening just once in a century) will occur four times in the life of an individual born in 1960 (once per 20 years). A child born in 2020 will experience that same extreme heat wave 20 times (if the Paris targets are met) to 40 times (if governments merely follow through with current climate policies, resulting in 3°C or 5.4°F global warming) in his or her lifetime (once every two to four years), depending on the ambition and success of climate policy solutions.

The authors note that policy choices and future warming pathways will not significantly alter extreme heat exposure frequency for people born before 1980; those changes are already baked in. But today’s climate policy decisions could dramatically alter the world 0f the youngest (and yet-to-be-born) generations.

Other types of extreme weather

The study authors also considered changes in extreme wildfires, crop failures, droughts, river floods, heat waves, and hurricanes. These types of events are not so directly impacted by rising temperatures. For example, the amount of water vapor in the atmosphere rises by 7% per 1°C or 2°F of warming, in turn amplifying flooding in flood-prone regions. As a result, future changes are projected to be less severe than extreme heat waves.

The authors concluded, “For a 3°C [5.4°F] global warming pathway, a six-year-old in 2020 will experience twice as many wildfires and tropical cyclones, three times more river floods, four times more crop failures, five times more droughts, and 36 times more heat waves” compared with a person born in the 1800s. For every one of these weather categories, people born after 1980 will experience more extremes than those born in the 1800s even if global warming is limited to 1.5°C (2.7°F).

There are also important regional variations, for example in terms of potential crop failures. In colder countries, agricultural production may benefit from higher temperatures, but the opposite is true in hotter regions like Central America, Africa, and the Middle East. Study co-author Stefan Lange of the Potsdam Institute for Climate Impact Research noted via email: “Countries for which we project larger increases in crop failure also tend to have larger population fractions working in agriculture, so the livelihood of more people depends on those yields projected to decline.”

American citizens and policymakers especially concerned about current levels of immigration across the southern border likely will find it troubling that crop failures in Mexico and Central America are projected to approximately double between the 1.5°C and 2.5°C scenarios. Imagine the resulting migration pressures in scenarios where the Paris targets are breached and regional crop failures become commonplace.

Policy and economics relevance

To justify new climate regulations, U.S. federal agencies must evaluate costs and benefits. The benefits, in terms of avoided climate damage costs, are quantified through the “social cost of carbon,” estimates of which are strongly dependent on what’s known as the “discount rate.” The discount rate reflects the fact that in a growing economy, money saved and invested today will accrue interest (usually estimated at a rate around 3% per year), and thus saving money is given more value than spending it.

But for intergenerational problems that threaten economic growth, that logic does not necessarily hold. A growing number of economists thus argue that the discount rate applied to climate policy should be substantially lower than current market interest rates. For example, in a February 2021 working paper, economists Nicholas Stern and Joseph Stiglitz argued,

“Models incorporating risk and time discounting support the use of an effective discount rate for evaluating climate projects that is small – smaller than the normal social rate of discounting. If there are important possibilities of catastrophic climate change in the future and very low living standards for those who survive, social rates of discount could be negative.”

The Trump administration had moved in the opposite direction, reducing the federal social cost of carbon estimate to near zero by applying discount rates as high as 7%. As Stern and Stiglitz noted,

“The consequences of using a high interest rate, even 7%, are obvious: a dollar in 50 years is worth 3 cents, a dollar in a hundred years is worth 0.1 cent: implying we should essentially do nothing to avoid large calamities a hundred years from now.”

The new Science paper helps quantify these choices in real-world terms. Discounting the welfare of future generations and threats they will face from climate change impacts will result in children born today experiencing substantially more extreme heatwaves, droughts, wildfires, floods, crop failures, and hurricanes during their lifetimes.

All of which may add ammunition to recent research suggesting that young people increasingly have a “we don’t trust you” attitude toward tepid governmental climate actions they largely see as a betrayal and as a failure to protect their generation.