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Humans Bring On Many Changes, Most Are Far From Painless

The views expressed are those of the author and are not necessarily those of Scientific American.

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From atmospheric changes, to timelapse imagery from Google Earth…our planetary presence is hard to miss.

This past week has seen the concentration of carbon dioxide (CO2) in Earth’s atmosphere reach a level of 400 parts-per-million, a value the planet hasn’t seen since several million years ago. To put this into some kind of context let’s take a look at the variation in CO2 over the past half century or so – via the classic ‘Keeling Curve‘.

Atmospheric CO2 concentration in parts per million as a function of time (Scripps/NOAA).












There are two basic features of this plot. First is that it wiggles up and down on an annual basis. That’s because the Earth has seasons and oceans and landmasses with living organisms that absorb and generate CO2. Plants, for example, tend to absorb CO2 in summers when they’re growing, and can release CO2 in winters when they’re rotting or dormant. The planet is also lopsided in the sense that there is more ‘habitable’ continental land mass  in the north than in the south – otherwise the net contribution to CO2 variation between northern summer and southern winter, or vice versa, would cancel out.

The second feature of this plot is that CO2 concentration is increasing with time. Why? Well, it’s simple, it’s because of us. This is seen most starkly if we take a look at a rather longer timeline – made using ice-core measurements of atmospheric CO2 (since our ancestors weren’t monitoring the atmosphere for us). It begins going uphill just around 1760 – the start of the Industrial Revolution.

CO2 concentration back to the 1700s - it starts rising around 1760 (Scripps)

You can begin to see just how steep the rate of change has become since the mid 20th century if we go even further back and look at the past 800,000 years.

See that little spike at the right hand side up to 400 ppm? That’s us, today. Although CO2 concentrations have been far from stable over the past 800,00 years, they take a sharp upward turn right in line with the rise of industrialized human civilization.

CO2 atmospheric concentrations from ice core sampling - for past 800,000 years (Scripps).

Now of course the ice core data are not perfect, there could potentially be some other spikes in there that get washed out in the measurements, but we would probably spot anything like our present fast rise.

How far back do we need to look to hit similar CO2 levels to today’s? It’s not quite clear, but it might be around 3 to 4 million years. A study by Bartoli, Honisch, and Zeebe in 2011 measured boron isotopes in the mineral shells formed by types of plankton, and suggests this was the case.

Looking further back, across more of the immense history of the planet, and we see that CO2 wanders all over the place. For example, here are some estimates showing both measurements and computer models (timeline flipped from previous plots).

500 million years of CO2 concentration on Earth (This figure was prepared by Robert A. Rohde from published data and is incorporated into the Global Warming Art project).











There’s a lot of uncertainty, but it’s clear that even our present 400 ppm CO2 concentration is small compared to what it has been tens to hundreds of millions of years in the past. Amounts that were five to twenty times higher than today seem more like the norm.

But humans, and the world we find around us, didn’t exist back then. These were periods where the Earth, our lovely home planet, would have felt about as alien as some of the exoplanets we’re now discovering in the surrounding universe. The environmental chemistry, the fauna (not always any flora), and the climate may have never before been a match for what it has been the past million years or so.

Like it or not, the historically low trough in the CO2 concentration of yesterday is a defining characteristic of the window of opportunity where our peculiar ape-related ancestors managed to get a foothold. The fascinating but rather terrifying thing is that we’ve now gone global, and we’ve learned how to extract vast amounts of energy from our environment, driven by an extraordinary ability to innovate and survive. By doing so we’ve altered that window, significantly changing the chemical composition of the atmosphere. And although I’m not going to discuss it in detail here, simple physics tells us what’s going to happen next. You cannot deny basic thermodynamics.

This is merely one change our presence has brought to the planet. There are many others. In fact you can now be a first-hand witness to the visible alterations going on around the globe through the magic of Google Earth. Terabytes of imaging data from 1984 to the present have been stitched together to allow a timelapse view of just about any part of the world. Go check it out here.

Even in this day and age of planetary awareness it’s pretty amazing to see just how infested a place it is. Here’s an example, Las Vegas, 1984 to 2012.

What happens in Vegas apparently spreads from Vegas....

Once you’re done with looking at other examples, try entering your own search…it’s quite educational.

Is it all doom and gloom? Yes and no. Clearly we’re testing the limits, we have a good chance of pushing our planet (if we haven’t done so already) to a place it hasn’t been to for millions of years – the kind of place that we might not like. The kind of place that might kill us. But we’re also amazingly clever, or else we wouldn’t know that we’re doing this. So what’s going to happen?

I wish I knew. But as a scientist, and an optimist, I can’t help but notice that if we’re serious about looking for life beyond the Earth and if we’re serious about looking for complex, technological life, it’s this kind of filthy disregard for planetary equilibrium that we should be sniffing for. We might have to wait a while if we find suitable candidate worlds to aim our telescopes at, but it’s conceivable we might catch some other life-form making precisely the same mistakes we are.

Through early morning fog I see
Visions of the things to be
The pains that are withheld for me
I realize and I can see

That suicide is painless
It brings on many changes
And I can take or leave it if I please

(Johnny Mandel and Michael Altman, ‘Suicide Is Painless’/M.A.S.H. theme)

Caleb A. Scharf About the Author: Caleb Scharf is the director of Columbia University's multidisciplinary Astrobiology Center. He has worked in the fields of observational cosmology, X-ray astronomy, and more recently exoplanetary science. His books include Gravity's Engines (2012) and The Copernicus Complex (2014) (both from Scientific American / Farrar, Straus and Giroux.) Follow on Twitter @caleb_scharf.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. erbarker 9:32 am 05/13/2013

    Is it true that the Mauna Loa CO2 observatory is located four miles down wind from an active volcano, spewing CO2?

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  2. 2. Caleb A. Scharf in reply to Caleb A. Scharf 9:43 am 05/13/2013

    1) The Mauna Loa atmospheric observatory is above the inversion layer and local phenomena – also ‘down wind’ is clearly not a constant thing. 2) Its measurements tally with dozens of other monitoring sites across the globe, including those in antarctica, 3) these data all tie in to ice core data, no manipulation, the data just match up.

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  3. 3. sault 12:28 pm 05/13/2013

    I’m pretty sure more climate deniers will try to post their long-debunked nonsense, so I’m going to pre-debunk ALL of it by directing people to this site:

    These deniers are either wittingly or unwittingly spreading unscientific nonsense that does not stand up to scrutiny. The goal is to disrupt as many climate and energy discussions as possible while giving the average person the perception that there is a lot more doubt in the scientific community about climate change than there really is. This way, the fossil fuel companies behind this propaganda campaign can keep the air as their own personal dumping ground for as long as possible. Actally cleaning up their act and preserving a recognizeable climate for future generations would hurt quarterly profits and they won’t stand for it!

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  4. 4. M Tucker 3:18 pm 05/13/2013

    “Clearly we’re testing the limits, we have a good chance of pushing our planet (if we haven’t done so already) to a place it hasn’t been to for millions of years” AND FASTER than it has ever been pushed before. That is the important part. It is the speed of the change that we humans are forcing on our civilization that is so destabilizing. It is hard for nature, and human civilization too, to keep up. Even with the climate change that we did evolve with we are nothing like our ancestors. The technology of our ancestors is largely extinct from the planet. The plants we depend on are largely monocultures designed to work in a narrow temperature range with lots of synthetic fertilizers, insecticides and herbicides. The animals too are bred to live in a stable climate that is compatible with the last 10,000 years. Our extraordinary success has come with a great price: no other creature, and no other past civilization, requires so much of Earth’s resources to sustain itself and creates such a vast waste stream as do modern humans.

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  5. 5. jduringer 4:03 pm 05/13/2013

    Mr. Scharf,

    Well presented global history, but your condescending tone for our species is a bit shrill – “filthy disregard”? And while projecting our experience on your search for ET isn’t totally unreasonable, have you no appreciation for how adaptable life (as we know it) is and the diversity of ecosystems? Not that I claim to know anything about it, but I’d figger looking for WOW signals would be far better than trying to discern other planets’ ecosystems are out of “balance”. You’d probably be better off trying astrology.

    Sault and Scharf, your moralizing is so over. Just cementing your rank in the holier than though church? Hand wringing is pretty good on stage. Are you also riding your bamboo bicycles around between jet rides to important meetings/vacations?

    Don’t you think the planet is well past the tipping point – the poles melting and massive amounts of decomposing biomass? Are you hallucinating to think your withering pronouncements will be slowing down developing world CO2 production?

    Our species has come up with some impressive technology for hellish conditions – weapons of war and such. Plenty of spin offs. Doubtless you won’t surrender your bully pulpits, but maybe you’ll put on your swim trunks and enjoy the warm weather and the technological innovation it will spawn.

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  6. 6. rkipling 4:12 pm 05/13/2013

    Unlike some, I have no problem with people, who genuinely anticipate catastrophic climate change, advocating that something be done to avoid catastrophe. I would just advocate that they do something other than talk.

    I’m an engineer. To better understand the scale of the problem, I attempted to calculate the time and capital required to maintain current world consumption of energy using alternative means which reduce atmospheric CO2 concentrations. I have also researched similar efforts by those with a far better grasp of the problem than I have. My conclusion was that the time and money required is in fact monumental compared to any previous project attempted by mankind. There is no point in arguing the specific number. It’s huge. But don’t take my word for it. Take the time to estimate the cost yourself.

    Some try to cast it as a question of spending massive amounts of money in the near term or spending massive amounts later after a catastrophe has happened. My observations of how governments work over the last 60 years do not give me any expectation that meaningful changes will be made regardless of the evidence presented. So, since I don’t believe sufficient resources actually can or will be diverted to this problem, alternative solutions must be found. (By the way, I don’t consider that age necessarily imparts wisdom.)

    My point isn’t to say that since it is so expensive let’s not bother to solve it. The point is that there is virtually no hope that those resources can or will be applied using current technology. The immediate negative impact on world economies would have governments either voted out of office or overthrown. It is unrealistic to expect the vast majority of the world’s population to be sufficiently forward thinking to make such sacrifices. Millions are already hand to mouth as it is.

    I think it’s great that alternative energy projects are underway. Take a look at the magnitude of impact they will have on atmospheric CO2 concentrations. Those projects will hardly be noticeable. Increase them by a factor of 10, same answer.

    So, where does that leave us? Our only hope isn’t Obi-wan Kenobi. It is as yet unknown technology for energy generation, CO2 sequestration, both? My thought is that rather than spending time preaching to the converted or apostates (as some obviously consider them), commenters should apply their efforts to find solutions.

    If there is a way to avoid the catastrophe some expect, game changing technology at a price acceptable to the average world inhabitant is likely the only thing that has a chance of stabilizing CO2 concentrations. Otherwise we will get what we get.

    Now, I don’t consider myself sufficiently knowledgeable to predict what will actually happen because of increasing CO2 concentrations. One thing that I’m pretty confident of is that CO2 won’t be reduced by comments on these blogs.

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  7. 7. RSchmidt 4:25 pm 05/13/2013

    “One thing that I’m pretty confident of is that CO2 won’t be reduced by comments on these blogs.” so that is an either/or case is it? One can only either comment on blog or do something about it. No one can do both. I guess that is why the problem is so hard to resolve.

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  8. 8. rkipling 4:30 pm 05/13/2013

    It clearly doesn’t suggest an either/or proposition.

    I do notice none of the other points were addressed.

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  9. 9. james wallace 7:57 pm 05/13/2013

    This from “Agent Smith” in The Matrix:

    “Every mammal on this planet instinctively develops a natural equilibrium with the surrounding environment but you humans do not. You move to an area and you multiply and multiply until every natural resource is consumed and the only way you can survive is to spread to another area. There is another organism on this planet that follows the same pattern. Do you know what it is? A virus. Human beings are a disease, a cancer of this planet.”

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  10. 10. jtdwyer 8:03 pm 05/13/2013

    The world’s population has more than doubled from 3 billion people in 1960 to >7 billion today. It’s expected to increase by another 2 billion people in the next 30 years before tapering off at 10 billion people.

    IMO, it’s unrealistic to think that, as per capita co2 production continues to increases, humanity can reduce atmospheric co2 levels through incremental change. Only through some unforeseeable technological breakthrough or catastrophic collapse can our destructive impact on the biosphere be significantly reduced.

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  11. 11. Quantumburrito 9:41 pm 05/13/2013

    “Only through some unforeseeable technological breakthrough or catastrophic collapse can our destructive impact on the biosphere be significantly reduced.”

    I vote for “catastrophic collapse”. I don’t see a technological breakthrough happening anytime soon.

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  12. 12. rkipling 11:08 pm 05/13/2013

    Well, CO2 concentrations are increasing. Whether that will result in a catastrophe is less certain.

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  13. 13. sault 1:16 pm 05/14/2013


    Those who resort to personal insults are obviously not interested in debating the facts. While it would be nice to think everything will be okay, we’ll all adapt to climate change and the ecosystems we depend upon will too, there is close to zero chance of that happening. Just look at how Hurricane Katrina reduced a major city in the world’s strongest country into a state of anarchy for a length of time. The only thing that brought it under control was a massive recovery effort coming in from unaffected areas of the country paid for by a stable central government. Increase the frequency / intensity of these storms along with more / worse droughts, wildfires, floods and a deteriorating geopolitical situation as most countries of the world experience the same sort if disasters and you have a big problem on your hands.

    And guess what, we’re cutting research budgets in a massive way just because a bunch of idiots on Wall St. made too many bad bets with tax-advantaged money. Imagine what will happen to all that technical innovation you think will swoop in and save us if we have to use the research funding to rebuild Manhattan or Miami instead.

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  14. 14. sault 1:33 pm 05/14/2013


    Why so reluctant to share the results of your “research” with us? I’d like to know what assumptions you made in your calculations. For starters, I’d like to know what value you placed on the social cost of carbon, or the damages that each ton of emitted CO2 is expected to cause over its lifetime. Central estimates place it at about $50 but some studies have it running as high as $900. It all depends on where the tipping points are in the climate and what time horizon you use. Again, I’d be interested in what value you placed on avoided future damages from climate change as a function of reduced emissions.

    I’d also like to know if you incorporated the damages of other fossil fuel pollution into your calculations. Several studies have determined that the pollution from coal power alone causes between $100B and $500B in damages to the U.S. economy every year due to negative health effects, increased healthcare spending, missed workdays, reduced worker productivity and premature death because of exposure to this pollution. And studies have linked urban air pollution from vehicles and power plants to a number of diseases including asthma, alzhiemers, strokes and a number of other maladies. Switching over to clean energy would free us from a lot of these burdens that we actualy pay for already, but they just don’t show up in the price of fossil fuels, making them artificially cheap.

    Finally, I’d like to know what balance of energy efficiency, demand management, renewable energy, nuclear energy and storage you used in your calculations and what you thought the cost for each was. Many energy efficiency improvements actually pay for themselves, so they would have a NEGATIVE cost. For example, efficient lighting, better insolation and a number of energy-saving approaches can pay for themselves in a matter of months to 1 or 2 years, providing a return on investment for the remainder of their useful life. Solar PV reduces peak power demand, allowing utilities to stop using as many inefficient “peaker” power plants all while reducing the pressure on grid bottlenecks since it can generate power at the point of load. Renewable energy like solar and wind also have zero fuel cost, lowering wholesale electricity prices due to the merit order effect.

    I just find it strange that you claim the cost to do all this is huge while experts much smarter than you or I have determined that large areas such as New York State can switch to over 99% renewable energy at costs similar to todays:

    “…a new study finds that it is technically and economically feasible to convert New York’s all-purpose energy infrastructure to one powered by wind, water and sunlight (WWS). The plan, scheduled for publication in the journal Energy Policy, shows the way to a sustainable, inexpensive and reliable energy supply that creates local jobs and saves the state billions of dollars in pollution-related costs.”

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  15. 15. Cramer 4:07 pm 05/14/2013


    Don’t you understand? rkipling doesn’t need to show his “research.” All you need to know is that he is an engineer.

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