Environment

23rd century CO2 levels could surpass the age of the dinosaurs

23rd century CO2 levels could ...
If left unchecked, by the year 2250 the Earth's atmospheric CO2 concentrations could hit levels not seen since the dawn of the dinosaurs, some 200 million years ago
If left unchecked, by the year 2250 the Earth's atmospheric CO2 concentrations could hit levels not seen since the dawn of the dinosaurs, some 200 million years ago
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Researchers have used plant fossils, such as this Ginkgo leaf, to determine ancient CO2 concentrations and plot out a record spanning back over 420 million years
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Researchers have used plant fossils, such as this Ginkgo leaf, to determine ancient CO2 concentrations and plot out a record spanning back over 420 million years
If left unchecked, by the year 2250 the Earth's atmospheric CO2 concentrations could hit levels not seen since the dawn of the dinosaurs, some 200 million years ago
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If left unchecked, by the year 2250 the Earth's atmospheric CO2 concentrations could hit levels not seen since the dawn of the dinosaurs, some 200 million years ago

The Earth was a very different place some 200 million years ago when the first dinosaurs began to emerge during the Triassic Period. The climate was hot and dry, with atmospheric carbon dioxide levels sitting at about 2,000 parts per million (ppm) – far higher than our current level of about 405 ppm. But a new study suggests that if emissions are left unchecked we could be on track to return to those CO2 levels in the next few centuries, and with a little help from a brighter, hotter Sun, surface temperatures on Earth could soar to new heights.

Climate change skeptics often argue that the atmosphere's greenhouse gas concentrations have always fluctuated. That's true: levels have been known to jump around from about 200 to 400 ppm during colder periods (such as our present time), up to thousands of parts per million in warmer times, but this happens on a scale of millions of years. Our current rate of increase is much faster than growth through natural causes.

A new study by researchers at the University of Southampton built up a picture of the CO2 concentrations over the past 420 million years. The record is compiled from more than 1,200 points of data in the form of fossilized plants and shells, and the carbon isotopic concentration of soil and oceans.

"We cannot directly measure CO2 concentrations from millions of years ago," says Gavin Foster, lead author of the study. "Instead we rely on indirect 'proxies' in the rock record. In this study, we compiled all the available published data from several different types of proxy to produce a continuous record of ancient CO2 levels."

Researchers have used plant fossils, such as this Ginkgo leaf, to determine ancient CO2 concentrations and plot out a record spanning back over 420 million years
Researchers have used plant fossils, such as this Ginkgo leaf, to determine ancient CO2 concentrations and plot out a record spanning back over 420 million years

With this detailed picture of the planet's atmospheric past, the researchers were able to track the natural CO2 fluctuations, and clearly spot the sudden uptick since the industrial era began. But greenhouse gases don't work alone in creating Earth's climate: our good friend the Sun plays a significant role as well, and in the past these two factors have worked against each other to keep the climate relatively stable.

"Due to nuclear reactions in stars, like our Sun, over time they become brighter," says Dan Lunt, co-author of the study. "This means that, although carbon dioxide concentrations were high hundreds of millions of years ago, the net warming effect of CO2 and sunlight was less. Our new CO2 compilation appears on average to have gradually declined over time by about 3-4 ppm per million years. This may not sound like much, but it is actually just about enough to cancel out the warming effect caused by the sun brightening through time, so in the long-term it appears the net effect of both was pretty much constant on average."

Projecting the data forward, the researchers predict that if humanity burns all fossil fuels that are available, atmospheric CO2 concentrations could shoot past 2,000 ppm by the year 2250. That would return us to levels not seen since the early days of the dinosaurs, but with one big difference: the Sun is brighter nowadays. The two factors would this time work together to heat the Earth's climate to unprecedented temperatures.

"Because the Sun was dimmer back then, the net climate forcing 200 million years ago was lower than we would experience in such a high CO2 future," says Foster. "So not only will the resultant climate change be faster than anything Earth has seen for millions of years, the climate that will exist is likely to have no natural counterpart, as far as we can tell, in at least the last 420 million years."

The research was published in the journal Nature Communications.

Source: University of Southampton via Science Daily

13 comments
DFrancis
Why no mention of Earth's dominant greenhouse gas? (FYI, it's water vapor.)
watersworm
In a "few centuries", anyway, no more petrol, no more gas, no more coal, so why scaring present people ? Or is it only against present POTUS'policy ? Or against lack of interest from the majority of people (The Paris COP21 is over, guys), more akeen on employment, poverty, education or health (some "insignifiant" items) ?
Bob
Yawn. What about all the other possible ways man can and will destroy himself. Little things like over-population, starvation, plagues, antibiotic resistant diseases, and war. Destroy the world economy by shutting down fossil fuels if you like but mankind, left to his own devices, is pretty well screwed anyway. Any species that overpopulates will eventually crash big time. I always wanted a pet dinosaur. I guess I was just born too late or too soon.
ripshin
Even the most cursory of reviews, and application of the most basic level of critical thinking skills, should make one question the assumptions so glibly presented as facts in this article. Shall we list them? - Hot dry climate at 2,000 ppm CO2: With the well documented and repeatedly observed effects of CO2 on plant life (high growth rates, ease of spreading, etc) and the abundance of water, it's inconceivable to me that the climate would be "hot and dry" at this level of CO2. It's just silly to think that, and is based on trying to sell the story that increased CO2 is going to lead to some kind of global desert. - Current rate of increase of CO2 much faster than natural: IIRC, Richard Alley demonstrated with the Greenland ice cores that CO2 levels can fluctuate quite rapidly, and that the climate response to transients doesn't just occur over millenial time scales. Furthermore, without knowing the precise correlation mechanisms the researchers used, I would still offer that the resolution of their timescales with these proxies is completely insufficient to state that CO2 levels take millions of years to change. Meaning, 1200 data points to cover some hundreds of millions of years leaves a LOT of time in between data points for things to change. - CO2 is the control lever that single-handedly cancels out the change in brightness of our sun: Our climate is a multi-variate chaotic system. Yes, it appears to be bounded, but it's still chaotic within those boundary domains. So...multi-variate means there are more than one variable that affects the system. Chaotic means, simply, that you don't get a linear response to changes in inputs. (Really, this is, or shouldn't be, that controversial...it's just well established math and physics.) So combine the "multi-variate" with the chaotic, and you simply can NOT state that increase in one variable will necessarily produce a specific outcome. I mean, come on people...this is some pretty basic stuff here. You don't have to be a climate scientist, a skeptic, or even that particularly invested in this debate to see through some of the more inane claims made here. rip
LarryWolf
Ripshin: Your right that it's wrong to assume higher CO2 means hotter and DRIER. The key word being drier. As temps go up, the relative humidity index goes up too--a lot. It's a common media misconception and lack of understanding of science that causes so much disinformation that people suck up and often it's wrong because the media are wrong because they are not scientists. In reality this is what happens as CO2 rises: https://www.skepticalscience.com/water-vapor-greenhouse-gas.htm CO2 and water vapor are BOTH greenhouse gases and water is short term and localized; CO2 is everywhere in the upper atmosphere and long term.
Daniel Boguszewski
The climate science now is Syfy science. Worthless study.
MartinVoelker
The article seems to highlight unimaginable temperature increases 200 years from now (when we're all dead) but let's understand that an increase to 600ppm in our current century - which is possible under business as usual plus some unpleasant feedback loops - is already threatening civilization, not just on the coasts where a quarter of humanity makes its living. As for the boilerplate denials arguments offered by other commenters I recommend visiting skepticalscience.org which presents a list of these arguments and what peer reviewed science has found on those. Those arguments are valid as a subject of inquiry but deniers ignore that obviously these valid questions have since been subjected to rigorous scientific inquiry. Because unlike people with an agenda, the international community of scientists simply wants to get it right, and its methods and structure are set up to do just that. And their consensus finds human caused climate change to be real and comparatively well understood.
f8lee
Hey, but think of how cool the fern like plants will look! Plus maybe there will be horse-sized dragonflies!
habakak
This is a pretty pointless exercise. If we are going to burn all the fossil fuels, we would realize that way in advance and plan on some alternatives. As short-sighted as people are, there are at least sufficient systems and numbers of people who are not. Besides, we invariably find another technology. And just based on what we know today of the increased economic viability of solar and wind energy, we do know that it is almost an impossible scenario that we will burn through all our fossil fuel supplies. Climate change is already being fixed. People are mostly too short-sighted to see it because there always is resistance to change. In 25 years we will look at this like young people today frown when you explain how scared the West was of USSR and the fear of the Cold War 3 decades ago.
Douglas Bennett Rogers
Added water will come out of the air in a few weeks but is added at a constant rate by desert irrigation. The global heat retention of CO2 of around 1 % is matched by a local heat retention of added water on 10 % of the land by around 30 %, which continues as long as the land is irrigated.