creation of a different planet, part 3

Preface, Part 1, Part 2, Part 3

measuring terraforming

Part 1 presents which nations have put most of the CO2 from fossil fuels into the atmosphere and who is doing most of it today. Part 2 places the top 25 CO2 emitting nations into 5 groups based on emissions per person. Here in Part 3 I look at one of the many ways we can measure human terraforming.

Anatomically modern humans appear in the fossil record in Africa about 130,000 years ago. DNA evidence places human origin about 70,000 years before that. [Smithsonian] This was at the end of the Pleistocene Epoch, the period from 1.8 million to 12,000 years ago during which the most recent episodes of global cooling, or ice ages, took place. By the end of this period humanity had spread throughout most of the world. [Berkeley]

The Pleistocene is followed by the Holocene Epoch (12,000 years ago to the present), geologically notable for being a relatively warm period in between ice ages. It also contains all of our recorded history, the creation of agriculture, and what we call civilization. During this time villages, towns, and cities appeared.

Humanity has greatly influenced the Holocene environment; while all organisms influence their environments to some degree, few have ever changed the globe as much, or as fast, as our species is doing. The vast majority of scientists agree that human activity is responsible for “global warming,” an observed increase in mean global temperatures that is still going on. Habitat destruction, pollution, and other factors are causing an ongoing mass extinction of plant and animal species; according to some projections, 20% of all plant and animal species on Earth will be extinct within the next 25 years. [Berkeley]

That quote describes terraforming — changing the atmosphere, temperature, surface topography or ecology of a planet, in this case, our planet. As one geologist, Andrew Gale of the University of Portsmouth, recently put it,

Human activity has become the number one driver of most of the major changes in Earth’s topography and climate. You can’t have 6.5 billion people living on a planet the size of ours and exploiting every possible resource without creating huge changes in the physical, chemical and biological environment which will be reflected dramatically in our geological record of the planet.

He and his colleagues will be asking the International Commission on Stratigraphy for formal adoption of the Anthropocene, the last 200 years, as the youngest epoch of the Earth’s geological timescale, arguing “that the dominance of humans has so physically changed Earth that there is increasingly less justification for linking pre- and post-industrialized Earth within the same epoch — the Holocene.”

Which brings us to CO2 emissions and climate change, the subject of this series. Our CO2 and other greenhouse gas emissions are causing the average global temperature to rise.

Jim Hansen writes that during the last 12,000 years,

The planet has been warm enough to keep ice sheets off North America and Europe, but cool enough for ice sheets on Greenland and Antarctica to be stable. Now, with rapid warming of 0.6°C in the past 30 years, global temperature is at its warmest level in the Holocene.

This warming has brought us to the precipice of a great “tipping point”. If we go over the edge, it will be a transition to “a different planet”, an environment far outside the range that has been experienced by humanity. There will be no return within the lifetime of any generation that can be imagined, and the trip will exterminate a large fraction of species on the planet.

Consider what 0.6°C means in the context of past temperature changes.

During the last 400 thousand years, we’ve had four ice ages separated by comparatively brief interglacials, warm periods in which the temperature was similar to today’s. The overall variation in temperature has been about 13 degrees C, from 4 above today’s temperatures to about 9 below.

(Note: This graph and the subsequent ones show deviation from the present temperature where present temperature is the global average temperature between 1960 and 1990.)

This graph of the last 150,000 years shows the last ice age and it’s bounding warm periods. In the most recent warm period, coinciding with the Holocene Epoch, humanity changed from a hunter-gathered lifestyle to an agricultural one based around villages, towns, and cities. Those units grew to city-states, nation-states, and now we have vast global networks of alliances and trading partners.

In the last 1,800 years the temperature has remained very stable until recently. Notice the change in scale on the vertical axis. It is now spans a total of only 1.1 degree C; on the previous graphs it was 15.0 degrees. (The curve shown is smoothed for readability. See the source graph, linked under references below, for more detail.)

Here in the detailed record of the last 150 years of temperature variation we can see why Jim Hansen calls “warming of 0.6°C in the past 30 years” rapid, and even when not rapid the trend is steadily upward — and has been for about the last 250 years about the time of the industrial revolution and the age of fossil fuels. While the growth in science, technology, and the arts has been impressive during this time, we have also seen the most violent wars and biggest genocides in human history, and the human population has increased by 500% since 1850.

Continuing the Hansen quote from above:

Casualties of passing this tipping point would include more than wildlife and indigenous ways of life in the Arctic, and the coastal environments and cities submerged by rising seas. The increased global warming would have world-wide effects via an intensified hydrologic cycle. In the U.S., for example, the great tier of semi-arid states from West and Central Texas, through Oklahoma, Kansas, Nebraska, and both Dakotas would likely become more drought-prone and ill-suited for agriculture. Africa will see a great expansion of dry areas. Large populations in Asia and South America will lose their primary fresh water source as glaciers disappear.

The crystallizing scientific story reveals an imminent planetary emergency. We are at a planetary tipping point. We must move onto a new energy direction within a decade to have a good chance to avoid setting in motion unstoppable climatic change with irreversible effects. The ‘dangerous’ CO2 level is at most 450 ppm, and it may be less. CO2 has already increased from pre-industrial 280 ppm to today’s 383 ppm, and it is now increasing about 2 ppm per year. Global disasters can still be avoided, but only if we act promptly.

Creation of ‘a different planet’, with an ice-free Arctic and eventual disintegration of ice sheets, can be averted only if planetary energy balance is restored at an acceptable global temperature, i.e., one that avoids these catastrophic changes. Estimates of permissible additional warming must be refined as knowledge advances and technology improves, but the upshot of crystallizing science is that the ‘safe’ global temperature level is, at most, about 1°C greater than year 2000 temperature. It may be less.

I had always thought of terraforming as the stuff of science fiction. In a Star Trek movie or a Ben Bova novel a barren planet is transformed into one with a rich biosphere by amazing human technology and effort. Instead, we’re going in the opposite direction, applying it haphazardly to a planet (Earth, the only one we have) with an incredibly rich biosphere and making it poorer. Worse, we call it progress.

references

How Can We Avert Dangerous Climate Change?, (18 page PDF) Jim Hansen, June 2007. State of the Wild: Perspective of a Climatologist (10 page PDF) (accepted, to be edited). For more of Hansen’s work see his web page at Columbia University and publications on his NASA Goddard page.

Sources for the global average temperature variation graphs:

• last 400,000 years
• last 150,00 years
• last 1,800 years
• last 150 years

Preface, Part 1, Part 2, Part 3