Increases in the abundance of atmospheric greenhouse gases since the industrial revolution are mainly the result of human activity and are largely responsible for the observed increases in global temperature [IPCC 2013]. However, climate projections have model uncertainties that overwhelm the uncertainties in greenhouse gas measurements. We present here an index that is directly proportional to the direct warming influence (also know as climate forcing) supplied from these gases. Because it is based on the observed amounts of long-lived greenhouse gases in the atmosphere, this index contains relatively little uncertainty.
The Intergovernmental Panel on Climate Change (IPCC) defines climate forcing as “An externally imposed perturbation in the radiative energy budget of the Earth climate system, e.g. through changes in solar radiation, changes in the Earth albedo, or changes in atmospheric gases and aerosol particles.” Thus climate forcing is a “change” in the status quo. IPCC takes the pre-industrial era (chosen as the year 1750) as the baseline. The perturbation to direct climate forcing (also termed “radiative forcing”) that has the largest magnitude and the least scientific uncertainty is the forcing related to changes in long-lived, well mixed greenhouse gases, in particular carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and halogenated compounds (mainly CFCs).
Atmospheric global greenhouse gas abundances are used to calculate changes in radiative forcing beginning in 1979 when NOAA's global air sampling network expanded significantly. The change in annual average total radiative forcing by all the long-lived greenhouse gases since the pre-industrial era (1750) is also used to define the NOAA Annual Greenhouse Gas Index (AGGI), which was introduced in 2004 [Hofmann et al., 2006a] and has been updated annually since.
What happens if the world went all out burning through the known reserves of fossil fuels - about five trillion metric tonnes? The likely results are frightening ... average global temperatures rise from 6.4° to 9.5°C and temperatures in the Arctic soar by as much as 19.5°C. This is much greater than earlier estimates and would result in widespread ecosystem collapses
The paper appears in Nature Climate Change (behind their paywall)
The climate response to five trillion tonnes of carbon
Katarzyna B. Tokarska1, Nathan P. Gillett2, Andrew J. Weaver1, Vivek K. Arora2 & Michael Eby1,3
1School of Earth and Ocean Sciences, University of Victoria 2Canadian Centre for Climate Modelling and Analysis, Environment and Climate Change Canada, University of Victoria 3Department of Geography, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
Concrete actions to curtail greenhouse gas emissions have so far been limited on a global scale1, and therefore the ultimate magnitude of climate change in the absence of further mitigation is an important consideration for climate policy2. Estimates of fossil fuel reserves and resources are highly uncertain, and the amount used under a business-as-usual scenario would depend on prevailing economic and technological conditions. In the absence of global mitigation actions, five trillion tonnes of carbon (5 EgC), corresponding to the lower end of the range of estimates of the total fossil fuel resource3, is often cited as an estimate of total cumulative emissions4, 5, 6. An approximately linear relationship between global warming and cumulative CO2 emissions is known to hold up to 2 EgC emissions on decadal to centennial timescales7, 8, 9, 10, 11; however, in some simple climate models the predicted warming at higher cumulative emissions is less than that predicted by such a linear relationship8. Here, using simulations12 from four comprehensive Earth system models13, we demonstrate that CO2-attributable warming continues to increase approximately linearly up to 5 EgC emissions. These models simulate, in response to 5 EgC of CO2 emissions, global mean warming of 6.4–9.5 °C, mean Arctic warming of 14.7–19.5 °C, and mean regional precipitation increases by more than a factor of four. These results indicate that the unregulated exploitation of the fossil fuel resource could ultimately result in considerably more profound climate changes than previously suggested.
Currently carbon dioxide emissions from shipping and airplanes is about six percent of the total. The problem is they appear to be on a path for a steep increase - partly from sector growth little emission improvements and partly from lower emissions elsewhere. The issues involved in reductions are tricky.
nternational transportation has been left out of U.N. agreements on fighting climate change because it does not fit easily into control regimes, such as the Kyoto Protocol and the Paris Agreement, which are based on national targets.
Which nation should be responsible, say, for a flight from Mexico City to New York, or a container ship heading from Shanghai to Los Angeles? Should the emissions be logged with the country where the plane or ship departs, or where it arrives, or according to its national flag or legal jurisdiction, or where it takes on fuel, or according to who or what is on board?
During the study 9,500 oblivious cinema goers sat down to watch films like The Hunger Games 2, Walking with Dinosaurs and The Little Ghost. The air composition inside the cinema was measured every 30 seconds using a proton transfer reaction mass spectrometer (PTR-MS) hooked into outgoing air vents. Over 100 chemical species were identified each time.
‘You might expect a vaguely changing mixture, but for many chemical compounds you get a nice consistent and reproducible correlation with events in the film,’ explains Jonathan Williams from the Max Planck Institute for Chemistry, who was one of the researchers involved. For instance, there were discernible spikes of isoprene twice during The Hunger Games 2, when the heroine’s dress catches fire and when the final battle begins. Isoprene is associated with muscle contraction—large spikes were also observed as people entered and left the cinema—so increases during the film could be due to unconscious muscle twitching as the audience empathises with the heroine, Williams suggests.
The paper appears in Nature and is outside their paywall
Cinema audiences reproducibly vary the chemical composition of air during films, by broadcasting scene specific emissions on breath
Jonathan Williams, Christof Stönner, Jörg Wicker, Nicolas Krauter, Bettina Derstroff, Efstratios Bourtsoukidis, Thomas Klüpfel & Stefan Kramer
Human beings continuously emit chemicals into the air by breath and through the skin. In order to determine whether these emissions vary predictably in response to audiovisual stimuli, we have continuously monitored carbon dioxide and over one hundred volatile organic compounds in a cinema. It was found that many airborne chemicals in cinema air varied distinctively and reproducibly with time for a particular film, even in different screenings to different audiences. Application of scene labels and advanced data mining methods revealed that specific film events, namely “suspense” or “comedy” caused audiences to change their emission of specific chemicals. These event-type synchronous, broadcasted human chemosignals open the possibility for objective and non-invasive assessment of a human group response to stimuli by continuous measurement of chemicals in air. Such methods can be applied to research fields such as psychology and biology, and be valuable to industries such as film making and advertising.
Air temperatures, on the one hand, are moderated by circulation—both the rising and sinking of air masses into the atmosphere, and the horizontal movement of winds across the landscape. Moisture also regulates how much heat can be stored in the air. “The value of the air temperature measurement, as opposed to land surface temperature, is that it is what the human body, a building, or an ecosystem are feeling,” says Stuart Gaffin, a climate researcher at Columbia University and NASA’s Goddard Institute for Space Studies. “Air temperatures largely dictate our thermal comfort level.”
On the other hand, land skin temperatures reflect the pure heating of a parcel of ground by radiation from the sun, the atmosphere, and other heat flows. Therefore, the hottest LSTs are likely to occur where the skies are clear, the soil is dry, and the winds are light. The final ingredient is the composition of the land surface. It should absorb most light and reflect little—that is, have a low albedo—and it should not conduct heat very well. Rocky deserts offer the perfect combination.
“This is not the first part of East Antarctica that’s likely to show a multi-meter response to climate change,” said Alan Aitken, the new study’s lead author and a researcher with the University of Western Australia in Perth. “But it might be the biggest in the end, because it’s continually unstable as you go towards the interior of the continent.”
The research — which found that Totten Glacier, and the ice system of which it is part, has retreated many times in the past and contains several key zones of instability — was conducted in collaboration with a team of international scientists from the United States, Australia, New Zealand and the United Kingdom. A press statement about the study from the U.S. group, based at the University of Texas at Austin, described the study as showing that “vast regions of the Totten Glacier in East Antarctica are fundamentally unstable.”
Indeed, the Totten Glacier watch has been ramping up lately: Scientists have already documented that warm ocean waters can reach the glacier’s base and that the enormous ice shelf that currently stabilizes it, extending over the top of the ocean, is melting from below. The glacier is thinning quickly, and its grounding line, where the ice shelf descends and meets the seafloor, has retreated inland three kilometers between 1996 and 2013 in some areas.
Finally, recent research has suggested that Totten can only lose a tiny 4.2 percent of its remaining ice shelf before the structure starts losing the ability to brace the larger glacier, holding it in place. It all points to a region of enormous vulnerability, and one that is already undergoing change.
In the south-east of Romania, in Constanța county close to the Black Sea and the Bulgarian border, there lies a barren featureless plain. The desolate field is completely unremarkable, except for one thing.
Below it lies a cave that has remained isolated for 5.5 million years. While our ape-like ancestors were coming down from the trees and evolving into modern humans, the inhabitants of this cave were cut off from the rest of the planet.
Despite a complete absence of light and a poisonous atmosphere, the cave is crawling with life. There are unique spiders, scorpions, woodlice and centipedes, many never before seen by humans, and all of them owe their lives to a strange floating mat of bacteria.