Saturday, April 6, 2013

How much will temperatures rise?

Runaway Global Warming

If we take the NASA Annual Mean Land-Ocean Temperatures and draw a projection into the future, temperatures will quickly be 3 degrees Celsius higher than the base period (1951-1980), i.e. well before 2050, as illustrated on image 1. below. 

Image 1. Temperatures will be 3 degrees Celsius higher well before 2050

Above projection appears to be steeper than even the worst-case scenario pictured by the IPCC for years, such as on the image below.

Image 2. from IPCC 2001. Projections of globally averaged surface temperature 2000-2100 are shown for six SRES scenarios and IS92a using a model with average climate sensitivity. The grey region marked "several models all SRES envelope" shows the range of results from the full range of 35 SRES scenarios in addition to those from a range of models with different climate sensitivities. The temperature scale is departure from the 1990 value.
Could temperatures rise faster in future than what the IPCC anticipated in 2001? The answer must be yes! In 2007, the IPCC described that, even if greenhouse gas concentrations in the atmosphere were stabilized for 100 years at year 2000 values (B1), then we would still be committed to a further warming of 0.5°Celsius. This committed warming should not be confused with ‘unavoidable climate change’ over the next half century, which would be greater because forcing cannot be instantly stabilized. And of course, as it turned out, emissions have not been stabilized at 2000 values, but have in fact increased substantially.

As it turned out, the models used by the IPCC made all kinds of assumptions that didn't eventuate. But before deciding to instead settle for a relatively simple extrapolation of observed data, there are some issues that require a further look.  

As discussed in the earlier post Accelerated Arctic Warming, temperatures in the Arctic have been rising at a much faster pace than global temperatures, and if this accelerated rise continues, we can expect a 10 degrees Celsius rise in the Arctic before 2040, as illustrated by image 3. below.  

Image 3. Three kinds of warming - 2: Accelerated warming in the Arctic 
Such a temperature rise in the Arctic will undoubtedly lead to additional greenhouse gas emissions in the Arctic, of carbon dioxide, nitrous oxide and particularly methane, threatening to trigger runaway global warming. 

The image below, from the methane-hydrates blog, combines these three kinds of warming, showing global temperatures that soon catch up with accelerated Arctic warming, as heatwaves at high latitudes will cause wildfires, in particular in Siberia, where firestorms in peat-lands, tundras and forests could release huge amounts of emissions, including soot, much of which could settle on the Himalayan plateau, darkening the ice and snow and resulting in more local heat absorption. Rapid melt of glaciers will then cause flooding at first, followed by dramatic decreases in the flow of river water that up to a billion people now depend on for water supply and irrigation.

In other words, the situation looks much more dire than what most models make us believe; the more reason to adopt the climate plan that is also described at the post at the methane-hydrates blog.

Image 4. Three kinds of warming - 1, 2 and 3 


- IPCC (TAR) - Climate Change 2001: Synthesis Report

- IPCC (AR4) - Climate Change 2007: Working Group I: The Physical Science Basis

- Accelerated Arctic Warming

- Methane hydrates


  1. Isn't runaway global warming already here? Isn't the evidence of this fact already found in the temperature record and positive feedbacks now occurring?

    There is also the massive methane releases being measured -- this doesn't happen unless we've already passed the tipping points.

    The IPCC cannot be considered the authority anymore on what will happen, due to their gigantic oversight (which was a deliberate political decision) and the years-long delay at publishing results.

    I am puzzled by the false optimism that I read online. There is nothing in the record to indicate this is justified other then "hopium". I think we are seriously deceiving ourselves at what has already occurred and what it means for our future.

  2. Really, Today is an all hands on deck moment to save Earth.
    We need to shield the Arctic from incoming radiation this year, get a handle on stopping methane release from sea floor and temperature rise. We need to stimulate the world's oceans by adding proper nutrients to stimulate biological productivity in an effort to both sequester carbon and to provide food for mankind.
    To do this effectively so Earth survives involves alteration to the value of money by Act of God'..
    The fact Antarctic is showing huge methane anomaly and Arctic is showing huge plumes of heat indicates time is short indeed to take action. If we can see what's obviously happening and mankind can act together and hold the peace in an effort to stop this in a full tilt attempt to zoom up economy and potential hope then our earth lives. But this is what needs war upon today.

  3. If the Arctic melted out this year, what changes would ensue in the projection to the increase in Arctic temperature and the onset of Runaway global Warming.

    I suppose things would happen somewhat sooner.

    1. The white line in image 4 gives a projection of how runaway global warming could eventuate, based on a business-as-usual scenario. As you say, things could happen sooner, e.g. if the Arctic melted out this year, which is within the margin of errors of projections based on observations, or if seismic activity in the Arctic caused hydrate destabilization and subsequent release of huge amounts of methane into the atmosphere.

    2. What timescale would you give for that?

      Would the amount of time taken be cut in half, for example the runaway occurs in around 2020 or something along those lines, or would it happen during the months following the melt out or earth quake in the Arctic.

    3. Quite frankly, I think we're just lucky that methane has as yet not entered the Arctic atmosphere in large quantities. Shakhova et al. in 2008 considered release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time. By comparison, the total amount of methane currently in the atmosphere is about 5 Gt. Back in 2002, Malcolm Light, contributor to this blog, warned about the hazard of seismic activity in the Arctic at a Geophysical Congress on methane hydrates, earthquakes and global warming (see poster at the bottom of this post).

  4. One thing I am becoming aware of is that senior writers in the Earth science community (eg Tim Lenton and Will Steffen) distinguish between "tipping points" (TP) and "tipping elements" (TE). In their writing and thought, positive feedbacks such as release of old carbon from the Arctic may be a TE , but not a TP. Tipping points are much larger events, eg transition to an ice free world. I think this is confusing.

    The following paper may avoid both terms - at least the abstract does: van Huissteden J, Dolman AJ. Soil carbon in the Arctic and the permafrost carbon feedback. Current Opinion in Environmental Sustainability. 2012; 4(5): 545-51.

    Lenton in a new paper (Lenton T. Arctic Climate Tipping Points. AMBIO. 2012; 41(1): 10-22) states: "There is widespread concern that anthropogenic global warming will trigger Arctic climate tipping points. The Arctic has a long history of natural, abrupt climate changes, which together with current observations and model projections, can help us to identify which parts of the Arctic climate system might pass future tipping points. Here the climate tipping points are defined, noting that not all of them involve bifurcations leading to irreversible change. {CB comment - if so then they would seem more TEs?} Past abrupt climate changes in the Arctic are briefly reviewed. Then, the current behaviour of a range of Arctic systems is summarised. Looking ahead, a range of potential tipping phenomena are described. This leads to a revised and expanded list of potential Arctic climate tipping elements, (CB: sic) whose likelihood is assessed, in terms of how much warming will be required to tip them. Finally, the available responses are considered, especially the prospects for avoiding Arctic climate tipping points"

    Or, more clearly, in Lenton TM. Early warning of climate tipping points. Nature Climate Change. 2011; 1: 201-9.): A climate ‘tipping point’ occurs when a small change in forcing triggers a strongly nonlinear response in the internal dynamics of part of the climate system, qualitatively changing its future state. Human-induced climate change could push several large-scale ‘tipping elements’ past a tipping point. Candidates include irreversible melt of the Greenland ice sheet, dieback of the Amazon rainforest and shift of the West African monsoon. Recent assessments give an increased probability of future tipping events, and the corresponding impacts are estimated to be large, making them significant risks. Recent work shows that early warning of an approaching climate tipping point is possible in principle, and could have considerable value in reducing the risk that they pose."

    Lenton et al's best known paper on this topic is probably Lenton TM, Held H, Kriegler E, Hall JW, Lucht W, Rahmstorf S, et al. Tipping elements (sic) in the Earth’s climate system. Proceedings of the National Academy of Science USA. 2008; 105(6): 1783-5.

    This refers to TEs yet the map in that paper seems to suggest large-scale transformations..

    To me it seems a matter of degree, with TE at one end of the spectrum and TP at the other - and everything in between being a mixture - but I think many people will use the two terms as synonyms

    BTW there is very little published on the "ecosocial" TPs likely to arise from Earth system TEs/TPs; I am working on that.