Thank God for CO2
It has been vilified in the press and maligned in school classrooms by the ignorant. Opposing it has become a cause célèbre in Hollywood an a litmus test for liberal politicians. Labeled man's chosen weapon for ravaging nature and laying waste to the environment this poor, largely misunderstood gas is in fact essential to our existence. Without carbon dioxide, CO2, we would not be here and Earth would be a frozen lifeless chunk of rock. Forget that life would never have developed on a planet without greenhouse warming, a recent scientific study say the daemon gas has rescued the planet from the deep freeze at least twice during the Neoproterozoic era, roughly 750 to 635 million years ago.
These days it is fashionable to agonize over the extent of polar ice packs, but those who do are naive if they think they know what “normal” levels of ocean ice are. Geological evidence suggests that marine ice extended to the Equator at least twice in the run up to the blossoming of complex life on Earth. That our planet was nearly or completely frozen from pole to pole is called the Snowball Earth hypothesis by climate scientists. In “Dynamics of a Snowball Earth ocean,” Yosef Ashkenazy and colleagues relate the possibility that ocean circulation and mixing processes would have set the melting and freezing rates that determine ice thickness, which in turn would have influenced the survival of photosynthetic life.
Their report, appearing in the journal Nature, does not explain why a Snowball Earth climate occurred but rather how life managed to survive such a freeze over. Note that the marine ice they are talking about is not the wimpy pack ice we see covering the Arctic ocean and surrounding Antarctica today. On Snowball Earth the oceans are covered by 200 meter thick floating glaciers. Here is a paragraph from the paper giving the authors' motivation:
The flow of thick ice over a Snowball Earth ocean (“sea glaciers”, characterized by dynamics very different from that of thinner sea ice), has received significant attention over the past few years. Similarly, the role and dynamics of atmospheric circulation and heat transport, CO2 concentration, cloud feedbacks, and continental configuration have been studied, as has the role of dust over the Snowball Earth’s ice cover. In contrast, despite its importance, the ocean circulation during Snowball Earth events has received little attention. The few studies that used full-ocean General Circulation Models concentrated mostly on the ocean’s role in Snowball Earth initiation and aftermath. No studies accounted for the combined effects of thick ice cover and flow, and driving by geothermal heating.
Note that things were different on planet Earth 700 million years ago: the life in the oceans was not the same as today and the continental land masses were distributed differently. Still life managed to survive—perhaps due to the type of dynamic circulation proposed by the authors—biding its time until the ice began to melt. What Ashkenazy et al. do not explain is how a Snowball Earth could occur and, more importantly, how one might end.
For scientific speculation regarding the waxing and waning of such planetary deep freezings consider the article “A 'snowball Earth' climate triggered by continental break-up through changes in runoff,” by Yannick Donnadieu et al., which appeared in Nature in 2004. Here is the paper's abstract.
Geological and palaeomagnetic studies indicate that ice sheets may have reached the Equator at the end of the Proterozoic eon, 800 to 550 million years ago, leading to the suggestion of a fully ice-covered 'snowball Earth'. Climate model simulations indicate that such a snowball state for the Earth depends on anomalously low atmospheric carbon dioxide concentrations, in addition to the Sun being 6 per cent fainter than it is today. However, the mechanisms producing such low carbon dioxide concentrations remain controversial. Here we assess the effect of the palaeogeographic changes preceding the Sturtian glacial period, 750 million years ago, on the long-term evolution of atmospheric carbon dioxide levels using the coupled climate–geochemical model GEOCLIM. In our simulation, the continental break-up of Rodinia leads to an increase in runoff and hence consumption of carbon dioxide through continental weathering that decreases atmospheric carbon dioxide concentrations by 1,320 p.p.m. This indicates that tectonic changes could have triggered a progressive transition from a 'greenhouse' to an 'icehouse' climate during the Neoproterozoic era. When we combine these results with the concomitant weathering effect of the voluminous basaltic traps erupted throughout the break-up of Rodinia, our simulation results in a snowball glaciation.
It should also be noted that there was a lot more carbon dioxide in the atmosphere back then, and a good thing too. A more powerful greenhouse effect was needed to prevent a planetary freeze up given the weaker output from the younger Sun. Rodinia was an ancient supercontinent that contained almost all of the world's continental land mass.
Rodinia was the dominant landmass of the Earth for at least 350 million years when it began to breakup around 750 million years ago. That breakup changed the carbon cycle in such a way the CO2 was sucked out of the atmosphere at an accelerated rate, reducing the amount in the atmosphere by 1,320 ppm (today there is only about 390 ppm of CO2 in the atmosphere). As CO2 levels plummeted so did temperatures. Soon Earth look like the illustration below.
Snowball conditions persisted for ten or more million years, caused by the precipitous removal of CO2 from the atmosphere—perhaps a lesson for those nascent geoengineering types who want to “cleanse” Earth's modern atmosphere by removing carbon dioxide. What pulled Earth back from its icy stupor? Most scientists think that volcanoes eventually replenished the CO2 in the atmosphere, enough so the ice melted around the equator and photosynthetic life came roaring back.
Over time, the continents once again formed a single large land mass, this time called Pangaea, and the rest is history. What caused these ancient super Ice Ages to come and go? Donnadieu et al. sum it up in a single sentence: “Long-term (greater than or equal to 106 yr) evolution of the partial pressure of atmospheric CO2 (pCO2) is controlled by the relative importance of degassing through volcanic and mid-ocean-ridge processes and the consumption of CO2 through continental silicate weathering.”
Scientists think that volcanoes ended the Snowball Earth super ice ages.
But isn't this what the climate alarmists have been prattling on about for four decades, that CO2 will cause temperatures to rise, endangering us all? Hardly. The levels of atmospheric CO2 we are discussing here is many times that of even the wildest IPCC future projections. While it is clear that the carbon cycle does help regulate Earthly temperatures, the greenhouse gas levels involved in the dramatic events of the past were much greater than today's variations. Here is what the Snowball Earth paper found:
[U]sing a complex model and quantifying the effect of the break-up, we predict a marked reduction in the concentration of CO2 in the atmosphere to a persistently low value in the range 400–630 p.p.m. on timescales of >10 Myr. We also find that model-predicted DC CO2 values are in the range of radiative forcings, resulting in the build-up of ice sheets at latitudes greater than 30°. These CO2 concentrations are just above the threshold value required to trigger a snowball Earth with the GEOCLIM model, that is, 250 p.p.m.
According to this study, the low range that allows for the onset of an ice age is between 400–630 ppm—again note that today's “elevated” level is around 390 ppm. Notice that the danger level, the tipping point to trigger the plunge into a Snowball Earth, is 250 ppm, not far below the “preindustrial” level often cited as desirable by climate alarmists of around 280 ppm. Below is a figure from the paper showing changes in atmospheric CO2 levels during the time in question.
Atmospheric CO2 history during the time period preceding the Sturtian snowball event.
Here SC denotes supercontinent configuration and DC dispersed land mass configuration. Shown are steady-state atmospheric CO2 levels achieved by the GEOCLIM model for the SC runs, for the SC runs with the inclusion of basaltic provinces (denoted SC trap), and for the DC runs also with basaltic provinces (denoted DC trap). The horizontal dashed lines denote the exact CO2 values reached by the model for the standard runs. The vertical arrow displays the change of the radiative forcing from direct CO2 effects alone. The dark blue area shows the CO2 levels required for a globally glaciated state under the 750 Myr-ago climate simulations used by the researchers. The dotted lines denote the range of atmospheric CO2 levels required for low-latitude glaciations as predicted by a diverse array of climate models and are here for comparison with the threshold obtained by the GEOCLIM model.
While it is true that humans have added to atmospheric CO2 levels the increase has not been anywhere near the amounts seen in the ancient past. And given the small levels of GHGs in-play today, CO2 is not the only feedback mechanism acting on climate change. In a report to be published in Nature Geoscicence, sea ice surrounding Antarctica is reported to have expanded slightly in the past few years. A combination of observations and climate model simulations suggests that cooling of the surface ocean by meltwater from the Antarctic ice shelves has contributed significantly to this sea ice expansion. According to R. Bintanja et al., sea ice surrounding Antarctica has expanded, with record extent in 2010.
“We present observations indicating that melt water from Antarctica’s ice shelves accumulates in a cool and fresh surface layer that shields the surface ocean from the warmer deeper waters that are melting the ice shelves,” they report. “This powerful negative feedback counteracts Southern Hemispheric atmospheric warming.”
Shown above are sea-ice extent trends (a) based on a combination of data from the final analysis, the preliminary analysis and near-real-time data (2009–2012) from Bintanja et al.. SST data (b) were taken from the National Centers for Environmental Prediction (NCEP) merged satellite data set and the in situ SST data set SST OI v2. The green line represents the 10-year running mean. Does this look like global warming to anyone? In fact, it reinforces the wide spread admission that global warming has been halted for the past 15 years.
The lack of global warming in the face of ever rising CO2 levels has been a bitter pill for warm-mongering climate alarmists to swallow. Even such global warming cheerleaders as the UK's Telegraph and the Economist have been forced to admit things are not going according to the climate alarmists' script. As reported in the Economist:
OVER the past 15 years air temperatures at the Earth’s surface have been flat while greenhouse-gas emissions have continued to soar. The world added roughly 100 billion tonnes of carbon to the atmosphere between 2000 and 2010. That is about a quarter of all the CO₂ put there by humanity since 1750. And yet, as James Hansen, the head of NASA’s Goddard Institute for Space Studies, observes, “the five-year mean global temperature has been flat for a decade.”
The article goes on to pronounce the mismatch between rising greenhouse-gas emissions and not-rising temperatures to be among the biggest puzzles in climate science. “Flat though they are, temperatures in the first decade of the 21st century remain almost 1°C above their level in the first decade of the 20th,” the anti-carbon news rag rants. “But the puzzle does need explaining.”
Part of the puzzle is why anyone should think that temperatures during the first decade of the 20th century were in some way more “normal,” more correct than the temperatures today. Why not the average temperature during the Medieval Warm Period, or the height of the Eemian, or the end of the Jurassic? When you chose arbitrary standards of comparison you can come up with any bogus result desired.
Ed Hawkins, of the University of Reading, points out that surface temperatures since 2005 are already at the low end of the range of projections derived from 20 climate models (see the chart). If they remain flat, they will fall outside the models’ range within a few years. That would mean the models are wrong. Since the models, which have been under development for decades, are based on mainstream climate theory it would mean that the theory is also wrong. Then all those who ranted about the dangers of anthropogenic global warming would stand revealed as either fools or charlatans.
Not that they are throwing in the towel—climate change true believers' faith is stronger than that. Of course, what they believe, or the climate change alarmists say has precisely zero impact on what the climate actually does.
Earth's climate is a dynamic balancing act, with some mechanisms trying to warm the planet and others trying to cool it. For the Past 30 million years or so cooling has been in the ascendency and make no mistake, we will return to glacial conditions on the future. The reassertion of ice age conditions will be burden enough for Earth's creatures and human civilization. If the planet were to continue cooling, descending into another snowball Earth period practically none of today's biota would survive.
This could be Tahiti during another Snowball Earth.
Instead of being demonized, CO2 should be celebrated. It keeps our planet livable and nurtures the plant-life that makes the air breathable and all other life possible. Modern day levels of carbon dioxide, far from being alarmingly high, are dangerously low. All the residents of Earth who are currently enjoying the temperate Holocene warmth should thank God for CO2. And if history is our guide, unless we wish to bequeath future generations a frigid hell to live in, we need to keep burning those fossil fuels.
Be safe, enjoy the interglacial and stay skeptical.