Humans may be reversing the climate clock, by 50 million years

A composite image of the Western hemisphere of the Earth. Credit: NASA

Our future on Earth may also be our past. In a study published Monday (Dec. 10, 2018) in the Proceedings of the National Academy of Sciences, researchers show that humans are reversing a long-term cooling trend tracing back at least 50 million years. And it's taken just two centuries.

By 2030, Earth's is expected to resemble that of the mid-Pliocene, going back more than 3 million years in geologic time. Without reductions in our greenhouse gas emissions, our climates by 2150 could compare to the warm and mostly ice-free Eocene, an epoch that characterized the globe 50 million years ago.

"If we think about the future in terms of the past, where we are going is uncharted territory for human society," says the study's lead author, Kevin Burke, who conducted the work while a graduate student in the lab of paleoecologist John "Jack" Williams, professor of geography at the University of Wisconsin-Madison. "We are moving toward very dramatic changes over an extremely rapid time frame, reversing a planetary cooling trend in a matter of centuries."

All of the species on Earth today had an ancestor that survived the Eocene and the Pliocene, but whether humans and the flora and fauna we are familiar with can adapt to these rapid changes remains to be seen. The accelerated rate of change appears to be faster than anything life on the planet has experienced before.

The new study builds upon work Williams and colleagues first published in 2007, which compared future climate projections to historical climate data from the early 20th century. The new study relies on extensive data about climate conditions to probe much deeper in Earth's geologic past and expand those comparisons.

"We can use the past as a yardstick to understand the future, which is so different from anything we have experienced in our lifetimes," says Williams. "People have a hard time projecting what the world will be like five or 10 years from now. This is a tool for predicting that—how we head down those paths, and using deep geologic analogs from Earth's history to think about changes in time."

During the Eocene, Earth's continents were packed more closely together and averaged 23.4 degrees Fahrenheit (13 degrees Celsius) warmer than they are today. Dinosaurs had recently gone extinct and the first mammals, like ancestral whales and horses, were spreading across the globe. The Arctic was occupied by swampy forests like those found today in the southern U.S.

In the Pliocene, North and South America joined tectonically, the climate was arid, land bridges allowed animals to spread across continents and the Himalayas formed. Temperatures were between 3.2 and 6.5 degrees Fahrenheit (1.8 to 3.6 degrees Celsius) warmer than they are today.

For the study, Burke and Williams—along with colleagues at the University of Bristol, Columbia University, University of Leeds, NASA Goddard Institute for Space Studies and the National Center for Atmospheric Research—examined the similarities between future climate projections as set forth by the Intergovernmental Panel on Climate Change Fifth Assessment Report and several periods of geologic history.

These included the Early Eocene, the mid-Pliocene, the Last Interglacial (129 to 116 thousand years ago), the mid-Holocene (6,000 years ago), the pre-industrial era (before A.D. 1850) and the early 20th century.

They used Representative Concentration Pathway 8.5 (RCP8.5), which represents a future climate scenario in which we do not mitigate greenhouse gas emissions, and RCP4.5, a scenario in which we moderately reduce greenhouse gas emissions, and climate simulations using three different but well-established models: the Hadley Centre Coupled Model version 3, the Goddard Institute for Space Studies ModelE2-R and the Community Climate System Model.

While not without their flaws, each of these models represents the best available data and state-of-the-art techniques.

Under both scenarios and across each model, compared to previous eras, the Earth's climate most closely resembled the mid-Pliocene by 2030 (under RCP8.5) or 2040 (under RCP4.5). Under the greenhouse gas stabilization scenario of RCP4.5, the climate then stabilizes at mid-Pliocene-like conditions, but under the higher of RCP8.5, the climate continues to warm until it begins to resemble the Eocene in 2100, achieving Eocene-like conditions more broadly by 2150.

The models showed these deep-geological climates emerging first from the center of continents and then expanding outward over time. Temperatures rise, precipitation increases, ice caps melt and climates become temperate near the Earth's poles.

"Madison (Wisconsin) warms up more than Seattle (Washington) does, even though they're at the same latitude," Williams explains. "When you read that the world is expected to warm by 3 degrees Celsius this century, in Madison we should expect to roughly double the global average."

The study also showed that under RCP8.5, "novel" climates emerge across nearly 9 percent of the planet. These are conditions that do not have known geologic or historical precedent and they concentrate in eastern and southeastern Asia, northern Australia and the coastal Americas.

"Based on observational data, we are tracking on the high end of the emissions scenarios, but it's too soon to tell," says Burke. "We may be somewhere between RCP4.5 and RCP8.5, though if we increase our climate mitigation efforts—like switching to renewable energy—we could find ourselves closer to the low end."

About a decade ago, Swedish scientist Johan Rockström and colleagues introduced the idea of "safe operating space," referring to the under which modern agricultural societies developed. By comparing to the deep past, Williams and Burke say, we are able to better understand the planetary boundaries and thresholds that delineate this space.

"The further we move from the Holocene, the greater the potential that we move out of safe operating space," says Williams, a faculty affiliate with the UW-Madison Nelson Institute Center for Climatic Research. "In the roughly 20 to 25 years I have been working in the field, we have gone from expecting climate change to happen, to detecting the effects, and now, we are seeing that it's causing harm. People are dying, property is being damaged, we're seeing intensified fires and intensified storms that can be attributed to climate change. There is more energy in the climate system, leading to more intense events."

In their paper, the researchers try to strike a balance between alarm and optimism. On the one hand, Earth is headed into the unknown in our children's and grandchildren's lifetimes. On the other, life has long proven to be resilient. And, Williams says, in many places we are moving away from fossil fuels toward more sustainable and carbon-free energy sources. But more needs to be done.

"We've seen big things happen in Earth's history—new species evolved, life persists and species survive. But many species will be lost, and we live on this planet," says Williams. "These are things to be concerned about, so this work points us to how we can use our history and Earth's history to understand changes today and how we can best adapt."

Explore further

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More information: K. D. Burke el al., "Pliocene and Eocene provide best analogs for near-future climates," PNAS (2018).
Citation: Humans may be reversing the climate clock, by 50 million years (2018, December 10) retrieved 24 May 2019 from
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Dec 10, 2018
humans are reversing a long-term cooling trend tracing back at least 50 million years

Utter and complete nonsense with no basis in science. There are no climate proxy records going back 50 million years with enough resolution to make that claim. Nor is there an accurate measure of how much humans may be "warming" the planet, if at all. Climate proxies are, at best, imprecise. The only thing that can be derived from them is (very) long-term cooling or warming trends, not absolute temperatures.

This is another in a long line of wildly speculative claims from alarmists, framed to appear scientific, based on nothing more than unverified assumptions about prehistoric temperatures and computer-generated climate models that are completely useless at predicting future temperatures. Unfortunately these untested hypotheses get repeated so often they transmogrify into received wisdom in the minds of the gullible, and even other scientists.

Dec 10, 2018
And yet it is published in the Proceedings of the US National Academy of Science.

I mean, just sayin'.

Dec 10, 2018

I mean, just sayin'.

Dec 10, 2018
And yet it is published in the Proceedings of the US National Academy of Science.

I mean, just brayin'......HAWW..HAWW...HEEE

The Da Snob jackass brays again.

IPCC officials admit mistake over melting Himalayan glaciers

Yet it was published in the IPCC report.

Dec 10, 2018
Global warming activist James Hansen has of course erased the 1910 to 1940 warmth.

Dec 10, 2018

Human and geological history tells us that it is always best to proceed on the side of caution, in spite of what the Climatolologists claim to know that any Global Warming is all the fault of humans, with only a short spurt from exploding volcanoes and other natural eruptions.
ClimatoLOLogists have a very heavy stake in this blame-game, since it is governments who are responsible for the making of new taxes to increase the wealth of the Climate Change aristocracy.
Therefore it is imperative to convince all governments to force their populations (of the western world) to drastically contribute their hard-earned money to the pockets/check and savings accounts of those scientists/politicians who bring the doom-and-gloom news to the public, in order to frighten them with the coming death of the planet - however untrue. Follow the money.

That doesn't alleviate the responsibility of humans to recycle and not pollute our waterways and atmosphere, of course.

Dec 10, 2018
@tehalgore bloviates again. You are seriously quoting the Grauniad? And you've got one quote from one scientist out of hundreds, in one paragraph of a multi-thousand page document?

That's all?


Dec 10, 2018
JUST IGNORE the climate change deniers. Their denialism posts are just complete GARBAGE! If you want pollution thrown in your face, look no further than Sur..Egg..Unit, askdad, or any of the other TRUMP supporters that infect the discussion area.

Dec 10, 2018
GW is nonsense and everyone knows it. Go to your safe space and have a good cry.

Dec 10, 2018
This is tedious. What's nonsense or can't you actually specify anything? Gonna cite teh algore or call me geigh?

Dec 10, 2018
It's AGW to you; @szore88. Pug-nose climate denier goon.

Dec 10, 2018

Officer goon; "we need to protect our coal interests"
Goon with boy goon; "anything to get rid of the human peasants"

Dec 10, 2018
It's AGW to you; @szore88. Pug-nose climate denier goon.
says howhot3

Resorting to nasty name-calling is typical of your bloviated cult of anti-human global warming/global cooling/global warming repetitious mantra that touts a huge 2 - 7 degree F. rise as the end of the world.
I have asked you before what do you intend to do with half of the 6 billion humans on Earth who continue to exhale CO2 gas from their bodies. You never provide an answer. So I will ask you again. What would you do to stop all of those humans from exhaling a GHG?

Dec 10, 2018
I have asked you before what do you intend to do with half of the 6 billion humans on Earth who continue to exhale CO2 gas from their bodies. You never provide an answer.
Even I can answer this. We let them keep exhaling-- because the carbon they exhale was only recently drawn from the atmosphere into the food they ate. This carbon is all rapidly recycling in and out of the atmosphere and isn't changing the carbon balance. The problem is digging up fossil carbon and burning it, which does change the atmospheric balance.

Dec 10, 2018
It seems if the observed rapid change in climate continues for several more hundred years, a new human species, substantially different, from Homo Sapiens might begin to evolve. Prevalent climate shaped the characteristics of animals in Pliocene, Eocene, and other epochs.

Dec 10, 2018
@Serv_EGG_U says;
what do you intend to do with half of the 6 billion humans on Earth who continue to exhale CO2 gas from their bodies.
Hummm... what a stupid question? I've been saying fossil fuel combustion and just about every conversation we've had. Where do you get human bodies from? It's obvious you don't know anything about the CO2 cycle, do you? So you're an idiot as well. To answer your question politely, @ddaye did it very well.

As far as you being a goon, you're a trump supporter so you are what you are (gooney to the goon goon).

Dec 10, 2018
Yes, whatever Carbon there is in, on, and under the Earth has been here since the Earth coalesced and formed into a full planet ~4.8 billions years ago. There has been no loss of that Carbon as it has changed form many times throughout geological history. Vegetation died, was buried, and became coal, gas or crude oil - the fats having seeped into the Earth to become crude.
However, humans and other animals have changed in form from CO2 breathing unicellular life forms, into Oxygen breathers; whereas plants have remained CO2 breathers and O2 exhalers/emitters.
Thus, it is the fault of Evolution that has caused humans/animals to exhale CO2 and not the fault of humans and animals, per se.

Dec 10, 2018
Due to the cycling and recycling of CO2, humans and animals have a very close symbiotic relationship with vegetation/trees. Humans emit CO2 and breathe O2, while trees/veg absorb CO2 and emit O2. A nice win-win situation.
So let us make the land masses of the whole Earth green again. The greenery could even absorb the CO2 from the oceans to save the sea life. Problem almost solved.
Then there is the conundrum of how to keep warm in winter and have electricity to run your appliances without using fossil fuels. Solar is no good at night, unless batteries are vastly improved. Wind power kills birds and may have undetermined consequences - unless way offshore.
So how to avoid using fossil fuels for warmth, appliances and travel?

Dec 10, 2018
@Surv_EGGs_Unit, You're just being ridiculous to be contrarian. So you know what the CO2 cycle is. We are impressed. You should be able to deduce from that that the combustion of fossil fuels releases what has been stored for millions and millions of years sequestered underground which adds to atmospheric CO2 levels in vast amounts. The situation now is we have a problem of excess production of CO2 to the point where the result will be calamitous to Mankind's survival (and planetary survival).

With regard to clean energy use you're an idiot if you don't pursue that model of energy production.

Dec 10, 2018
yes i remember the pliocene , very scary time

Dec 11, 2018
We haven't gotten to 1000 years ago.

Call me when the coast of Greenland is warm enough for barley for at least 400 years.

Dec 11, 2018
So either you are living in the tropics, or you keep your house/apartment cold to avoid using a fossil fuel and you pile your bed with extra blankets to keep warm, is that right?
You are afraid to turn the light switch to ON because that will start the electricity flowing to your lamps, which comes directly from the grid, which is powered by a plant that burns a fossil fuel, is that right?
You drive an electric car with a solar panel on the roof, but on cloudy days, you have to drive up to a station to charge your batteries. And where does that power come from to charge your car batteries? Why, from the grid, of course, which is powered by a plant that burns a fossil fuel, is that right?
And for entertainment, you don't watch the telly, because that requires electricity from the grid, which is powered by a plant that burns a fossil fuel, isn't that right, howhot?
And when you want to cook breakfast, lunch or dinner, you light a candle, isn't that right, howhot?

Dec 11, 2018
Soooo. Man is preventing an Ice Age..............................isn't that good or would you prefer living in an igloo? But then, we know how you all think about the human race, don't we, you'd like to see us go extinct...................but then where and how would YOU live. If humanity is your enemy, will you consider selficide?

Dec 11, 2018
This will happen by 2150. Sorry, but it will not happen. I say this because the author needs to spend some time on the website and read some of the work being done regarding quantum computers. They will be an estimated 100,000 to 1,000,000 times faster than current supercomputers. With AI and machine learning, these computers will find a way for humans to very easily control the climate.

Case in point: 'Electrogeochemistry' captures carbon, produces fuel, offsets ocean acidification - June 25, 2018, University of California - Santa Cruz

Key to speeding up carbon sequestration discovered

Chemists demonstrate sustainable approach to carbon dioxide capture from air – TechXplore - September 20, 2018 by Dawn Levy, Oak Ridge National Laboratory

CO2 being an issue is officially over:
"How to suck carbon dioxide from the sky for fuels and more"

All on

Dec 11, 2018
Humans will be able to control earths climate very likely by 2050 and almost for certain by 2060. The predictions of disaster by 2100 or 2150 are patently absurd on the surface.

Dec 11, 2018
"Humans will be able to control earths climate very likely by 2050 and almost for certain by 2060. The predictions of disaster by 2100 or 2150 are patently absurd on the surface."

Humans cannot even govern themselves with out creating wars. Yea, right, we can govern the climate without creating a huge disaster.

Dec 12, 2018
This comment has been removed by a moderator.

Dec 12, 2018
the sky is falling the sky is falling, excuse me while I barf

Yeah, yeah. More climate denier goonery. You bunch of pug-nosed climate deniers... acting all so holier-than-thou Climate change is going to get your gooney kids first, so you might as well go ahead and have that vasectomy you always wanted. You know, do the kids a favor and leave the world in a better place than you received it.

Dec 13, 2018
Interesting article, though it must be said that Seattle (47.6 deg. N) and Madison 43.0 deg. N) are not on the same latitude.

Dec 18, 2018
Just two facts for climate alarmist morons:
Sea level rise for last 100 years was approximately 30 cm
See level rise for last 20 000 years was approximately 120 meters (all of it without any real participation of humans, but humans survived it without any major problem)


Dec 29, 2018
...And by going back to these conditions pretty much spells the disruption of life as we know it everywhere, in what sense is this moral or ethical?

Sure, you can call the scenarios themselves alarmist- but in what sense is this process moral? And if there is no essential climate that need be preserved, is it not morally equivalent that, one day you wake up in a burning oven, everything around you dying, and I take some benefit for myself- what moral claims can you make against me? Can we seriously believe that we are entitled to change the climate to the detriment of the future generations- our children or grandchildren, and expect them to accept this as ethically sound? For me it is abhorrent, even devious.I see this as theft and vandalism, pure and simple. It matters not the degree of responsibility. No one with character or honor would act with such impudence. Our forebears might have had the excuse of ignorance, we do not.

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