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Nov 20, 2012

Why 4 degrees will end the world as we know it: World Bank

The World Bank has produced an alarming report that puts in context the risks of inaction on emissions reduction and climate change. It doesn't make for pleasant reading.

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The World Bank yesterday released a report prepared by the Potsdam Institute spelling out what the world is likely to experience if it warmed by 4 degrees — that’s looking increasingly likely by the end of the century without some serious policy changes by governments globally.

The report essentially attempts to summarise much of the research literature that has built up since the 2007 fourth IPCC Assessment Report and puts it in the context of the path we’re on unless we start taking this problem seriously. It doesn’t make for pleasant reading. World Bank President Dr Jim Yong Kim says “it is my hope that this report shocks us into action”, as he believes “a 4 degree world can, and must, be avoided”.

For the World Bank, with a primary purpose to help impoverished nations out of poverty, “the lack of action on climate change not only risks putting prosperity out of reach of millions of people in the developing world, it threatens to roll back decades of sustainable development”.

The chart below provides an impression of the alternative emission paths and their likely implications for temperature rise. According to the report, we are on a path illustrated by the red line. However, if governments follow through on the pledges they’ve made at the UN’s Copenhagen and Cancun summits then it would put us on the purple line, giving a mean temperature rise estimate of 3 degrees.

But even this path still carries a 20% chance of temperature exceeding 4 degrees. If governments don’t make good on their pledges then the red line would imply a 40% chance of warming above 4 degrees.

Median estimates of temperature rise from probabilistic projections for several scenarios

The latest research, unlike older assessments, is more confident that land-based ice, and not just thermal expansion of existing sea water, will play a significant role in sea level rise. Older assessments were hopeful that increased snow falls might occur over Greenland and the Antarctic that could offset any melting from higher temperature. Unfortunately, the rate of land ice contribution to sea level rise has increased by about a factor of three since the 1972–1992 period. And both the Greenland and Antarctic ice sheets have been losing mass since at least since the early ’90s.

The chart below illustrates that our current emissions path (the red line) gives a mean estimate of a one metre rise in sea level by the end of this century. However, sea level would continue to rise substantially after this point. For example, even if global warming was limited to 2 degrees, global mean sea level could still rise by between 1.5 and 4 metres above present-day levels by the year 2300.

Probablistic projections of sea level rise for different emission scenarios

Rising temperatures will lead to increased likelihood of extreme weather events and heat waves. The report notes that the past decade has seen an exceptional number of extreme heat waves around the world. These events — Victoria’s 2009 heat wave and associated severe bushfire; Russia in 2010 (which claimed 55,000 lives); Europe in 2003 (70,000 premature deaths); the US in 2012 — were highly unusual with monthly and seasonal temperatures typically more than three standard deviations warmer than the local mean temperature for that period.

Another well understood feature of this warming will be a strengthening of the hydrological cycle because a warmer atmosphere can hold more water vapour. This tends to exacerbate droughts and flooding rains.

The table detailed below documents a series of extreme events over the past decade and the degree of confidence that these could be attributed to human-induced climate change. Many of these events are so outside the bounds of past experience that it seems there is a medium to high likelihood that global warming has contributed to the event’s severity.

Note: numbered references available from page 18 of the report

These extreme events, in conjunction with rising overall temperature, will take their toll on agriculture. While modelling prior to 2007 predicted some improvement in food production with warming of 1 to 3 degrees, according to the analysis, “research since 2007 is much less optimistic”. The report observes:

“These new results and observations indicate a significant risk of high-temperature thresholds being crossed that could substantially undermine food security globally in a 4°C world.”

The effect of 4 degree warming would be disastrous for coral reefs. Coral reefs would stop growing at a CO2 concentration of about 450ppm, which we’re well on the way to hitting within the next few decades. And coral reefs are at high risk of dissolving by around 2050 unless we seriously turn our emissions growth around.

Those who aren’t inclined towards conspiracy theories already know this is a serious problem. This report simply provides an exclamation point on the already apparent urgent need for action.

*This article was originally published at Climate Spectator

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35 thoughts on “Why 4 degrees will end the world as we know it: World Bank

  1. Brent Hoare

    Mark Duffet @1 I suggest you go and read the report, and find some references that disprove the studies cited therein before making such sweeping generalisations. No wait, I’ll copy a relevant bit here for everyone:
    “Ocean Ecosystems
    “Disruption of the ocean ecosystems because of warming and ocean acidification present many emerging high-level risks (Hofmann and Schellnhuber 2009). The rising atmospheric carbon dioxide concentration is leading to rapid acidification of the global ocean. Higher acidity (namely, lower pH) of ocean waters leads to reduced availability of calcium carbonate (ara- gonite), the resource vital for coral species and ecosystems to build skeletons and shells.
    “The combination of warming and ocean acidification is likely to lead to the demise of most coral reef ecosystems (Hoegh-Guldberg 2010). Warm-water coral reefs, cold-water corals, and ecosystems in the Southern Ocean are especially vulnerable. Recent research indicates that limiting warming to as little as 1.5°C may not be sufficient to protect reef systems globally (Frieler et al. 2012). This is a lower estimate than included in earlier assessments (for example, the IPCC AR4 projected widespread coral reef mortality at 3–4°C above preindustrial). Loss of coral reef systems would have far-reaching consequences for the human societies that depend on them. Moreover, their depletion would represent a major loss to Earth’s biological heritage.” And it goes on…

  2. Ian

    Lets face it we have a problem…sorry, many, many problems and climate change in the medium to longer term is the mother of all problems but we are also rapidly running out of all sorts of resources, oil, fish and phosphorous to name but a few. Yes and the environment is being wrecked here in Australia and elsewhere.

    At the same time we have a peak debt problem. About the only thing not in short supply at the moment is money which they keep printing and feeding to the bankers, the military and so forth but not to you or I.

    We have the US and allies running wild looking to satisfy the needs of the military/industrial complex and we have the mainstream press ignoring or trivializing these problems and creating a culture of selfishness, ignorance and apathy.

    To be fair on Crikey, at least they do cover most of the issues in a more enlightened way but what we are all neglecting to discuss is why the problems continue and are, in fact, escalating. There is no simple answer to that but perhaps a start would be to recognize that our capitalist system is broken and our major parties as well as those in the the rest of developed world refuse to let go of it.

    We must realize that the relentless pursuit of growth, trickle down economics and the “free market” controlled by corporate monopolies or oligopolies will have a sad ending. I began to recognize the problem around about the time of the failed Copenhagen climate summit and events since then have reinforced my belief.

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