New study identifies causes of multidecadal climate changes

New study identifies causes of multidecadal climate changes
Global climate change threatens the continued existence of glaciers, such as the Aletsch Glacier in Switzerland, photographed in July 2015. Credit: Anupma Gupta/Michael Evans

A new reconstruction of global average surface temperature change over the past 2,000 years has identified the main causes for decade-scale climate changes. The analysis suggests that Earth's current warming rate, caused by human greenhouse gas emissions, is higher than any warming rate observed previously. The researchers also found that airborne particles from volcanic eruptions were primarily responsible for several brief episodes of global cooling prior to the Industrial Revolution of the mid-19th century.

The new also largely agrees with of the same time period. The researchers found agreement for caused by identifiable factors, such as volcanic aerosols and , as well as for random fluctuations in that take place on the same timescales. This suggests that current climate models accurately represent the contributions of various on —and are capable of correctly predicting future climate warming.

The research team—19 members of the Past Global Changes (PAGES) project, including University of Maryland Geology Associate Professor Michael Evans—used seven different statistical methods to perform the reconstruction. The results are published online July 24, 2019, in the journal Nature Geoscience.

"Our reconstructions look like the 'hockey stick' diagram of global temperature change that was first reconstructed more than two decades ago," said Evans, who is also co-chair of PAGES and has a joint appointment at UMD's Earth System Science Interdisciplinary Center (ESSIC). "Thanks to the work of the PAGES community, we have much more data now. The results were consistent regardless of how we created the reconstructions or which randomly chosen subset of input data we used."

The new 2,000-year reconstruction improves on previous efforts by using the most detailed and comprehensive database of its kind yet assembled. This dataset, painstakingly compiled by PAGES researchers, includes nearly 700 separate publicly available records from sources that contain indicators of past temperatures, such as long-lived trees, reef-building corals, ice cores, and marine and lake sediments. The data are sourced from all of Earth's continental regions and major ocean basins.

New study identifies causes of multidecadal climate changes
Graph shows global mean rates of temperature change over the last 2,000 years, as determined by a new reconstruction based on climate proxy data. Red denotes temperature increases while blue denotes temperature decreases. The green line shows the maximum expected warming rate without human influence; the dashed orange line signifies the ability of climate models to simulate this natural upper limit. The black line indicates average global as determined by direct measurements since the Industrial Revolution. Credit: University of Bern

By comparing the new reconstructions with existing climate simulations generated using the Coupled Model Intercomparison Project 5 (CMIP5) climate models, the PAGES research team was able to determine the relative contributions of several influences on global temperatures over time. These included natural influences, such as fluctuations in solar heating and the cooling effect of particles ejected by , as well as the human-caused influence of greenhouse gas emissions.

The results suggest that volcanic activity was responsible for variations before about 1850. After that, greenhouse gases became the dominant influence on global climate. By removing these influences in their analysis, the researchers also identified the magnitude of the random changes that cannot be traced to a specific cause. The team's data-based reconstructions also agreed with model simulations when evaluating these random changes.

"This makes us more confident that our reconstructions are realistic and, in turn, that the climate models are simulating past and future climate warming faithfully," Evans added.

This agreement between the researchers' data-based reconstructions and the CMIP5 simulations suggests that existing climate models can accurately predict future global temperature change over the next few decades, according to Evans. However, these simulations depend heavily on the choices that humans make in the future, which is very difficult to predict, Evans added.

"The uncertainty in the influence of human activities is not so large when looking forward only a few decades," Evans said. "But in the longer term, the choices we make for our energy sources and how much carbon these sources emit really matter."


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More information: Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era, Nature Geoscience (2019). DOI: 10.1038/s41561-019-0402-y
Journal information: Nature Geoscience

Citation: New study identifies causes of multidecadal climate changes (2019, July 24) retrieved 21 August 2019 from https://phys.org/news/2019-07-multidecadal-climate.html
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Jul 24, 2019
"This suggests that current climate models ... are capable of correctly predicting future climate warming."

And yet, climate models have so far spectacularly failed to correctly predict climate changes.

Jul 24, 2019
The analysis suggests that Earth's current warming rate, caused by human greenhouse gas emissions, is higher than any warming rate observed previously.


Nonsense. Nothing close to 8000 BCE
https://en.wikipe..._optimum

Still waiting for vineyards in Scotland and dairy cows on Greenland

Jul 24, 2019
Nonsense to your nonsense @shootit and @claudit You always give it away with your vineyards in Greenland, Scottland crap. You should both change your names to @debunked and play tiddlywinks to find out who wins the name. My favorite quote from the article is this;
This suggests that current climate models accurately represent the contributions of various influences on global climate change—and are capable of correctly predicting future climate warming.
So all you migbrain rightwinger climate denyin rusckiee lovers need to adventure into the great outdoors, inhale and take on some free-air.

Jul 24, 2019
So all you migbrain rightwinger climate denyin rusckiee lovers


Russians are right wing now? God are you a stupid fool.

Jul 24, 2019
same data , same result

Jul 24, 2019
Meanwhile the CIA/Pentagon is blaming Iran for manufacturing Plutonium, when in fact it was the USA that went over the critical mass limits imposed by Stephen Hawking and caused a critical mass explosion in a Plutonium forge that was meant to be decommissioned 25 years ago because it was not built to spec.

BAN PLUTONIUM!

Jul 24, 2019
Liar.. Liar.. Pants on fire...

"And yet, climate models have so far spectacularly failed to correctly predict climate changes." - Claudius

Climate models predict climate which for the purposes of discussing climate change is the average weather taken over 30 year periods.

Climate models haven't made predictions for the present since the present is less than 30 years from the period in which the models were created.

Predictions have been made typically for the period around 2100, and so far the global climate tracks well with the model trends.

So why did you feel a need to lie, Claudius?

Are you mentally ill?

Jul 24, 2019
"Nonsense. Nothing close to 8000 BCE
https://en.wikipe...optimum" - Shootist (moron)

Hay MORON. There is nothing in your link that discusses the rate of warming during the holocene.

Are you really that stupid?

LOL!

Even the graphic shown in the article you link to, shows how laughably stupid you are.

LOL!

Jul 24, 2019
It's obscene, for what idiots the AGW Cult takes their flock.
Gobble up Chicken Shites.


Jul 24, 2019
AGW doesn't exist, but the propagandists still disseminate their psychological terrorism.

https://www.zeroh...practice

Jul 24, 2019
Wow @vendicar, It's so good to hear from yah again, a fellow person that speaks truth to power, were power = BS trumpest flakes and russkie loven nut-zoids. @Old-C is certainly a russian spy or McConnell operative who is a specialist in misinformation. Same with the lot of them, and at the same time, they have their AC cranked to 74 and complain about AGW antifa.

Jul 24, 2019
"This suggests that current climate models ... are capable of correctly predicting future climate warming."

And yet, climate models have so far spectacularly failed to correctly predict climate changes.

I always wonder why the anti-science squad continues to repeat this myth when all data shows that it's incorrect. Climate models have done quite well in their projections (https://www.clima...vations/ ).

Jul 24, 2019
Wow @vendicar, It's so good to hear from yah again, a fellow person that speaks truth to power, were power = BS trumpest flakes and russkie loven nut-zoids. @Old-C is certainly a russian spy or McConnell operative who is a specialist in misinformation. Same with the lot of them, and at the same time, they have their AC cranked to 74 and complain about AGW antifa.

I leave mine at 80... And I'm Prussian...

Jul 24, 2019
leave mine at 80... And I'm Prussian...


Good one... but (and take this with a grain of your favorite grain...) don't tell them AGW deniers that. They might want to try to send you back... to Prussia.

Here is my favorite quote; the quote of the night.
"Our reconstructions look like the 'hockey stick' diagram of global temperature change that was first reconstructed more than two decades ago," said Evans, who is also co-chair of PAGES and has a joint appointment at UMD's Earth System Science Interdisciplinary Center (ESSIC).

I always thought "Hockey stick" straight up was the best description for climate change when compared to history, but I think this makes me think it might be more like a massive step up that won't go back except for extinction events of the source of AGW.

Jul 25, 2019
I had assumed these science news items were written by fairly intelligent, educated people. Silly me. I see the same mindless slagging-off nonsense that passes for "discussion". How depressing.

Jul 25, 2019
So all you migbrain rightwinger climate denyin rusckiee lovers


Russians are right wing now? God are you a stupid fool.

If you know anything about modern day Russia, it's right wing all the way. Discrimination againts gays and trans people, hatred against foreigners, fake news, money to the elites, all this is right wing stuff. Soviets might have been in the left but Russia is far right.

Jul 25, 2019
So all you migbrain rightwinger climate denyin rusckiee lovers


Russians are right wing now? God are you a stupid fool.


Umm...yeah! Where have you been since 2000? After the fall of the Soviet Union, Boris Yeltsin shifted Russia to the right, and when Putin took over in 2000, he quickly allied himself with the conservative Russian-Orthodox church and ever since, Russia has been ruled by the hard right. That is not even slightly controversial. Just look up the United Russia party.

If you seriously think the Russian government ISN'T hard right, your opinion is entirely baseless.

Jul 25, 2019
"Hard right" is not quite right. Russia and many other countries are now led by useful idiots spewing the rhetoric of international fascism, the bastard child of Nazi survival networks set up after 1945. Nazis called themselves the "Third Way," neither right nor left. So they said. Nazism was simply feudalism in modern garb.

Russia has had, since the days of Catherine the Great, a love/hate relationship with Germany. It's not surprising that with the collapse of communism, the vacuum would be filled by an imported authoritarian philosophy.


Jul 25, 2019
Yeah the perception of our Ruskie friends is that of skinhead alt-rightists lead by a bunch of shadowy Oligarchs that don't have any concept of human rights or freedom. Just Another Authoritarian Country Of Fanatical Fascists (JACOFF).

I've known many russian students and I know that is not who they are, but with the massive russian influence campaign of 2016, 2018 that has very successfully divided the country into extremist positions, makes the stereotype facists very real. Especially now that USA separates and imprisons children in concentration camps and lets them die beside toilets! Climate change is just a symptom of the extremist right-wing wealth drive takeover of humanity. It's the same lack of humanity that brought us into World War II and made it a just war to fight.

Jul 25, 2019
howhotnot , veery inteeresting , keep talking ,,,,,

Jul 26, 2019
Reconstructed warming"


Complete bullchit.

Jul 26, 2019
. @Old-C is certainly a russian spy or McConnell operative who is a specialist in misinformation.


And you're a mentally ill kid living in his Mother's basement.

Aug 03, 2019
@Old_C_Code:

You're not man enough to respond to a serious rebuttal of your bizarre claim that Russia is not a right-wing country.

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