BraveNewClimate

Guest post by Andrew Glikson and Emily Spence

(Andrew is an Earth and paleo-climate scientist, Australian National University who has contributed regularly to Brave New Climate. Emily Spence, environmental and social policy writer, Massachusetts, U.S.A.)

“Dear Caesar
Keep Burning, raping, killing
But please, please
Spare us your obscene poetry
And ugly music “
– From Seneca’s last letter to Nero

According to Albert Speer, German physicists, apprising Hitler of the possible development of an atom bomb in the spring of 1942, noted a reservation by Werner Heisenberg about a potential conflagration of the atmosphere: “Hitler was plainly not delighted with the possibility that the earth under his rule might be transformed into a glowing star.” The same awesome possibility, fusion of atmospheric nitrogen and oceanic hydrogen, turning the planet into a chain-reacting bomb, was considered a few months later by Edward Teller, Robert Oppenheimer, Arthur Compton, Hans Bethe and other physicists. New calculations indicated atmospheric conflagration was unlikely. The trinity nuclear test in the New Mexico desert went ahead.

A critical parameter in Drake’s Equation, which seeks to estimate the number of planets that host civilizations in the Milky Way galaxy, is L — the longevity of technological societies measured from the time radio telescopes are invented in an attempt to communicate with other planets. Estimates of L range between a minimum of 70 years and 10,000 years, but even for the more optimistic longevity scenario, only 2.31 such planets would exist in the galaxy at the present time.

It is another question whether an intelligent species exists in this, or any other galaxy, which has brought about a mass extinction of species on the scale initiated by Homo sapiens since the mid-18th century.

The history of Earth includes five major mass extinctions which define the ends of several periods, including the Ordovician, Devonian, Permian, Jurassic and Cretaceous periods. Each of these events has been triggered by extraterrestrial impacts, massive volcanic eruptions, or methane release and related greenhouse events. Yet, with the exception of the role of methanogenic bacteria in relation to methane eruptions in the past, the Sixth mass extinction is a novelty: For the first time in its history, the biosphere is in crisis through biological forcing by an advanced form of life, namely the activity of a technological carbon-emitting species.

The sharp glacial-interglacial oscillations of the Pleistocene (1.8 million years ago to 10,000 years ago), with rapid mean global temperature changes by up to 5 degrees Celsius over short periods of centuries and, in some instances, a few years (cf. Steffensen et al., Science Express, 19 June, 2008), culminated in an extreme adaptability of Homo. Of all the life forms on Earth, only this genus mastered fire, proceeding to manipulate the electromagnetic spectrum, split the atom and travel to other planets—cultural change overtaking biological change.

Possessed by a conscious fear of death, craving God-like immortality and omniscience, Homo developed the absurd faculty to simultaneously create and destroy, culminating with the demise of the atmospheric conditions that allowed its flourishing in the first place. The biological root factors which underlie the transformation of tribal warriors into button-pushing automatons capable of triggering global warming or a nuclear winter remain inexplicable.

(more…)

Filed under: Future | 9 Comments »

CO2-equivalents in 2005, for all forcings and just greenhouse gases

You may have heard that the planet is committed to further warming and sea level rise, irrespective of what choices we now make to reduce carbon emissions. The global warming century trend that was observed from 1906 to 2005 was 0.74°C (with a 90% uncertainty range of 0.56°C to 0.92°C), with more warming occurring in the Northern over Southern Hemispheres, and more over land compared to oceans. Yet, based on our understanding of the climate impact of greenhouse gases (GHG) such as carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O) and other trace gases, we should have observed even more warming than this. Actually, when you put all the pieces together, the expectation is for much more warming.

But before I tackle the critical issue of just how much more warming is still in the pipeline (in another post), it is important to explain the concept of carbon dioxide equivalents (CO₂-e). This term initially confuses a lot of people, but it’s not really that difficult to grasp once it’s been explained.

To start, you need to understand that from a global warming perspective, we are interested in the changes in GHGs – which causes an energy imbalance. The pre-industrial and current concentrations of well-mixed long-lived GHG are 278 parts per million (ppm) for CO₂ (now 383), 700 ppb (pp billion) for CH₄ (now 1,775), and 270 ppb for N₂O (now 320). Most of the other trace greenhouse gases (there are plenty), such as chloroflourocarbons (CFCs) and sulphur hexafluoride (SF₆), are almost exclusively a result of industrial activity. Now to quantify their relative contribution to global warming, we need to find a way of putting all of these individual gases (and other climate drivers) on an equal – or equivalent – footing. That’s where CO₂-e comes in.

The IPCC has two ways of expressing CO₂-e. The first is known as concentration equivalence, which has units of ppm CO₂-e. This definition asks: for a given change of a climate forcing agent (such as a greenhouse gas or aerosol), what change in the concentration of CO₂ would have been required to have the same effect as the additions of this forcing? ‘Effect’ is here defined in terms of radiative forcing (RF), which is (loosely) the change in the amount of incoming (to Earth) versus outgoing (to space) radiation/energy, measured in watts per square metre (w/m²). A positive RF warms, negative cools.

The other way of representing CO₂-e is by emission equivalence, which has units of the mass of CO₂-e per unit time. For instance, you could define the climate warming impact over a 100-year period of 1 million tonnes (Mt) of methane as being same as if you’d released 25 Mt of CO₂. If you shortened the time period to 20 years, that 1 Mt of methane would be the same as 72 Mt of CO₂. The difference between time periods is because methane is more powerful GHG than CO₂, but it breaks down more rapidly. This expression is also known as the global warming potential of a GHG.

(more…)

Filed under: Future | 25 Comments »