Effects of U.S.-China climate pact will be limited, scientists say

WASHINGTON – Don’t expect the landmark U.S.-China climate change agreement to nudge the world’s rising thermostat downward much on its own, scientists say.

While they hail it as a start, experts who study heat-trapping carbon dioxide don’t see the deal, announced Wednesday in Beijing, making significant progress without other countries joining in.

The math shows that even with the agreement, the globe still is rushing toward another 2-degree temperature rise – a level that world leaders have pledged to avoid as too dangerous.

China, the world’s No. 1 polluter, still will increase its emissions until 2030 or so, under the agreement. The U.S., which ranks second, promised to cut pollution from the burning of coal, oil and gas to levels that haven’t been seen since 1969. But whatever cuts the U.S. makes will be swamped by the Chinese growth in pollution over the next 15 years.

“It doesn’t change things much,” said Glen Peters, a Norwegian scientist who was part of the Global Carbon Project international team of researchers that tracks and calculates global emissions every year.

“This is not far off the business as usual” scenario the world is already on, he said.

In 2009, countries across the globe set a goal of limiting global warming to about another 2 degrees Fahrenheit (1 degree Celsius) above current levels. Peters’ team calculated earlier this fall that the world would hit that mark around 2040 and the U.S.-China accord doesn’t change that, he said. The numbers are just too big.

MIT professor John Sterman, who runs computer simulations of global emissions, said, “It doesn’t buy a lot of time for when we blast through the 2-degree level.” It may help in the long run when emission cuts pile up, he said, “but by then you’ve locked in sea-level rise, you’ve locked in more extreme weather, water shortages and declines in agricultural output.”

World leaders forged the first international treaty to combat global warming in Kyoto, Japan, in 1997. But developing countries, including China and India, were not required to reduce greenhouse gas emissions. The U.S. signed the agreement but did not ratify or honor it.

After only nonbinding goals were adopted in 2009 in Copenhagen and a U.N. summit earlier this year, international leaders now are aiming to forge a follow-up agreement in Paris in late 2015.

After Wednesday’s announcement, Climate Interactive ran simulations that showed the new agreement will mean about 700 billion tons of carbon dioxide will be kept out of the air by 2100, reducing expected cumulative carbon pollution by about 8 percent.

That would only prevent temperatures from rising about a third of a degree Fahrenheit (two-tenths of a degree Celsius), said Andrew Jones, co-director of the project at MIT. If all other countries followed the U.S.-China example, temperatures could be reduced by as much as 1.5 degrees Fahrenheit (0.8 degree Celsius).

In the agreement, China, whose emissions are rising as it builds new coal plants to fuel its economic growth, set a target for its emissions to peak in 2030 or earlier. That’s the first time China has set a deadline for stopping its emissions growth.

It’s not clear how high China’s emissions will go until the 2030 peak. But using recent growth rates and simple math, Peters calculated that China’s annual carbon emissions could grow by as much as 5 billion tons to 16 billion tons over that period.

In contrast, U.S. emissions will only go down about 1.2 billion tons by 2025 as a result of President Barack Obama’s pledge to reduce carbon pollution 26 percent to 28 percent below 2005 levels.