Rate of climate change ‘unprecedented’

BIG SKY, Mont. — People who are skeptical about climate change don’t particularly bother James Hurrell, director of the National Center for Atmospheric Research based in Boulder, Colorado.

He’s been doing climate research for 25 years and he’s heard most of what researchers and the public have to say on the topic.

“It doesn’t drive me nuts at all,” he said during a break at the International Bison Conference July 5.

“I think it’s really a communication issue and I think the scientific community needs to do a better job communicating what we know and what we don’t know about the problem. It’s a very complex topic and it can be a very confusing topic.”

Part of the confusion lies in the distinction between climate and weather, he said.

People know the difficulty of getting an accurate weather forecast so it logically follows that it is equally difficult, and potentially inaccurate, to predict climate for years, decades and centuries into the future.

Dannele Peck, director of the USDA’s northern plains climate hub, compares the difference between weather and climate to the difference between what a person is wearing today compared to the entire wardrobe they’ve ever owned. One is immediate and evident and the other reflects the past use plus future needs and possibilities.

That said, Hurrell said during his speech to bison producers that although climate is always changing, the current rate is “beyond the realm of natural variability.”

“The rate of change … that we are experiencing is unprecedented and it’s due to the human influence, the burning of fossil fuels and deforestation, primarily.”

Researchers and scientists have been monitoring and commenting upon rising atmospheric carbon dioxide levels since at least 1896, said Hurrell.

Now CO2 concentrations are at their highest in 800,000 years. Until about 18,000 years ago, at the end of the last ice age, CO2 concentrations never exceeded 290 parts per million.

Today, they are over 400 p.p.m. and are projected to be 900 p.p.m. by 2100 if things continue on the current trajectory.

“Assuming business as usual,” said Hurrell, the United States will be 2.75 C to 5.5 C warmer by the end of this century.

That will cause higher sea levels and affect millions of people. As one example of other consequences, Hurrell said 14 of the U.S.’s largest airports would be directly impacted by the rise in water level.

The biggest impacts will be felt through extreme weather events, he added. Floods will be larger and droughts longer lasting.

Taking action to reduce CO2 emissions and levels can limit the amount of warming but it might not be apparent in our lifetimes. Hurrell said even with mitigation measures enacted now, average temperatures will continue to rise because the oceans take a long time to cool.

“It’s going to take many years to undo what we’ve already done. Carbon dioxide has a very long lifetime in the atmosphere. I think the key point is that the trajectory that we’re on, if we do nothing about that, we’re really going to be experiencing rates of change that the planet has never experienced.

“By doing what we can, even as individuals, to limit the emissions … we can still avoid the most dire consequences of all of this.”

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