Is Climate Change Accelerating? Leading Scientists Clash On The Issue

Famed climate scientist James Hansen worryingly says
climate change is accelerating, but other top
scientists aren't so sure about that. 

Two of the nation's top climate experts are clashing politely on a subject that will deeply affect all of us

Are things bad, or really bad?

More specifically, is climate change accelerating, or is it still a steady, dreadful uphill climb?

Either option is of course sub-optimal  for us, to say the least. 

 If the world keeps warming at the pace it's been for the past several decades, we can expect more and longer deadly heat waves, worse storms, rising sea levels and politically destabilizing climate mass migration.  

If the pace of climate change is increasing, all of the above problems will be that much worse. 

This all started last week when famed former NASA scientist James Hansen said that the pace of climate change has steepened by 50 percent since 2010.  

Hansen, you might recall, first alerted the American public and put climate change front and center in the nation's conversation during dramatic Congressional testimony he provided back in 1988.

Hansen's main argument now is there is more sun energy in the atmosphere after 2010 thanks to efforts to cut pollution. The downside of less pollution are less sooty particles - known as aerosols - to bounce the sun's heat back out to space, so warming increases. 

As the Associated Press reports:

"Hansen's study said from 1970 to 2010, the world warmed at a rate of 0.18 degrees Celsius per decade, but projects that would increase to a rate of at least 0.27 degree Celsius per decade after 2010. NOAA data shows that 0.27 degrees is the rate since September, 2010."

So much goes on in the atmosphere, both via climate change and natural processes, it's easy to get into the weeds. It's hard to parse out what's a temporary thing, what's climate change, what's some other influence. 

There are bursts in which the global climate warming accelerates, and we are in one now. El Nino boosts global temperatures.  A record breaking volcanic eruption in Tonga back in January, 2022 threw an unprecedented amount of water vapor high up into the stratosphere. 

So, climate change, El Nino, and to a much lesser extent Tonga and new sulfur pollution rules are boosting this year's global temperatures  to what will be the hottest on record. 

Michael Mann, one of the world's leading climate
scientists, respects James Hansen but is highly
skeptical of Hansen's assertion that climate
change is accelerating. 

Another very strong El Nino occurred in 2015-16 and that boosted global temperatures to what were then record levels.

 El Nino transitioned to a cooler La Nina in the late 2010s and the first couple years of the 2020s, so the rate of warming temporarily leveled off somewhat during that period. 

After Hansen's study came out  another titan of climate change science, University of Pennsylvania scientist Michael Mann posted a rebuttal to Hansen. While careful to note he has deep respect for Hansen, Mann thinks Hansen's hypothesis is overblown.  

The Washington Post reports:

"Mann argued that the ocean's heat content is growing steadily, but  - in contrast to Hansen and his co-authors - is not accelerating. Mann also cited data showing that there does not appear to be a sudden shift in pollution from aerosols  over the past few years. Other researches have found a decline in aerosol pollution from cleaning up shipping would only shift global temperatures by 0.05 to 0.06 Celsius."

That said, Mann did note, "It has always been risky to ignore (Hansen's) warnings and admonitions." However, Manns also but also said of Hansen's new research: "The standard is high when you're challenging scientific understanding.....And I don't think they've met that standard, by a long shot."

Mann isn't exactly relaxed about the whole business of climate change though. The steady state increase  without an acceleration of the pace "is bad enough," he said. 

Another key difference between Hansen and Mann is that Hansen tiptoed into the realm of policy advocacy in his recent study. That's not typically what scientists do. Scientists will say "this is happening" and leave it to politicians, the public and the world in general to decide what to do about it. 

Hansen suggests some geo-engineering - namely deliberately putting those aerosols back up into the atmosphere to reflect sunlight. 

Mann is still old school. He doesn't believe scientists should put policy recommendations in their peer reviewed studies. Mann also thinks Hansen's geo-engineering ideas are actually dangerous and could backfire on humankind. 

All this must seem like a gossip column about scientists, or some weird click bait that gets views by highlighting conflict.

But the dispute between Hansen and Mann is in an odd way reassuring. It's how science is supposed to work. Scientists do fresh studies, other scientists question those studies. That yields further studies in an attempt to see who's right. All this is done without screaming matches or manufactured outrage. 

It's two respected scientists who respect each other, but disagree on one aspect of their work. That the two are trying to find more answers to climate change is good, even if the subject they're studying is very, very bad.