Tuesday, 15 March 2016

Abrupt climate change

Ten Degrees Warmer In A Decade?

11 March, 2016

In 2015, mean global carbon dioxide grew by 3.09 parts per million (ppm), more than in any year since the record started in 1959. An added polynomial trendline points at a growth of 5 ppm by 2026 (a decade from now) and of ppm by 2029.

NOAA data, added trend points at 5 ppm growth a decade from now

There are a number of elements that determine how much the total temperature rise will be, say, a decade from now:

Rise 1900-2016: In January 2016, it was 1.92°C (3.46°F) warmer on land than in January 1890-1910, as discussed in an earlier post that also featured the image 

Rise before 1900: Before 1900, temperature had already risen by ~0.3°C (0.54°F), as Dr. Michael Mann points out.

Rise 2016-2026: The image at the top shows a trend pointing at 5 ppm growth a decade from now. If levels of carbon dioxide and further greenhouse gases keep rising, then that will account for additional warming over the next ten years. Even with dramatic cuts in carbon dioxide emissions, temperatures will keep rising, as maximum warming occurs about one decade after a carbon dioxide emission, so the full wrath of the carbon dioxide emissions over the past ten years is still to come.

Removal of aerosols: With dramatic cuts in emissions, there will also be a dramatic fall in aerosols that currently mask the full warming of greenhouse gases. From 1850 to 2010, anthropogenic aerosols brought about a decrease of ∼2.53 K, says a recent paper. In addition, people will have emitted a lot more aerosols since 2010.

Albedo change: Warming due to Arctic snow and ice loss may well exceed 2 W per square meter, i.e. it could more than double the net warming now caused by all emissions by people of the world, calculated Professor Peter Wadhams in 2012.

Methane eruptions from the seafloor: ". . . we consider release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time," Dr. Natalia Shakhova et al. wrote in a paper presented at EGU General Assembly 2008. Authors found that such a release would cause 1.3°C warming by 2100. Note that such warming from an extra 50 Gt of methane seems conservative when considering that there now is only some 5 Gt of methane in the atmosphere, and over a period of ten years this 5 Gt is already responsible for more warming than all the carbon dioxide emitted by people since the start of the industrial revolution.

Water vapor feedback: Water vapour feedback acting alone approximately doubles the warming from what it would be for fixed water vapour. Furthermore, water vapour feedback acts to amplify other feedbacks in models, such as cloud feedback and ice albedo feedback. If cloud feedback is strongly positive, the water vapour feedback can lead to 3.5 times as much warming as would be the case if water vapour concentration were held fixed, according to the IPCC.

The image below puts these elements together in two scenarios, one with a relatively low temperature rise of 3.5°C (6.3°F) and another one with a relatively high temperature rise of 10°C (18°F).

Temperature rise on land a decade from now (without geoengineering)

Note that the above scenarios assume that no geoengineering will take place.

[ click on images to enlarge ]

As described above, the January 2016 temperature anomaly on land compared to January 1890-1910 was 1.92°C (3.46°F). Globally, the anomaly was 1.53°C (2.75°F), as shown by the image top right.

Putting the elements together for two global scenarios will result in a total rise of 3.11°C (5.6°F) for a relatively low global temperature rise and 9.61°C (17.3°F) for a relatively high global temperature rise, as shown by the image bottom right.

So, will climate catastrophe occur in a decade or later? There are many indications that the odds are large and growing rapidly. Some say climate catastrophe is inevitable or is already upon us. Others may like to believe the odds were rather small. Even so, the magnitude of the devastation makes it imperative to start taking comprehensive and effective action now.

The situation is dire and calls for comprehensive and effective action, as described in the 
Climate Plan.

No comments:

Post a Comment