Humanity's choice

Humanity’s choice (via IPCC): Aggressive climate action ASAP (left figure) minimizes future warming. Continued inaction (right figure) results in catastrophic levels of warming, 9°F over much of U.S.

The U.N. Intergovernmental Panel on Climate Change (IPCC) has issued its second of four planned reports examining the state of climate science. This one summarizes what the scientific literature says about “Impacts, Adaptation, and Vulnerability” (big PDF here). As with every recent IPCC report, it is super-cautious to a fault and yet still incredibly alarming.

It warns that we are doing a bad job of dealing with the climate change we’ve experienced to date: “Impacts from recent climate-related extremes, such as heat waves, droughts, floods, cyclones, and wildfires, reveal significant vulnerability and exposure of some ecosystems and many human systems to current climate variability.”

It warns of the dreaded RFCs (“reasons for concern” — I’m not making this acronym up), such as “breakdown of food systems linked to warming, drought, flooding, and precipitation variability and extremes.” You might call them RFAs (“reasons for alarm” or “reasons for action”). Indeed, in recent years, “several periods of rapid food and cereal price increases following climate extremes in key producing regions indicate a sensitivity of current markets to climate extremes among other factors.” So warming-driven drought and extreme weather have already begun to reduce food security. Now imagine adding another 2 billion people to feed while we are experiencing five times as much warming this century as we did last century!

No surprise, then, that climate change will “prolong existing, and create new, poverty traps, the latter particularly in urban areas and emerging hotspots of hunger.” And it will “increase risks of violent conflicts in the form of civil war and inter-group violence” — though for some reason that doesn’t make the list of RFCs.

AN OVERLY CAUTIOUS REPORT

As grim as the Working Group 2 report on impacts is, it explicitly has very little to say about the catastrophic impacts and vulnerability in the business as usual case where the Earth warms 4°C to 5°C [7°F-9°F] — and it has nothing to say about even higher warming, which the latest science suggests we are headed toward.

The report states:

  • “Relatively few studies have considered impacts on cropping systems for scenarios where global mean temperatures increase by 4°C [7°F] or more.
  • “… few quantitative estimates [of global annual economic losses] have been completed for additional warming around 3°C [5.4°F] or above.”

D’oh! You may wonder why hundreds of the world leading climate experts spend years and years doing climate science and climate projections, but don’t bother actually looking at the impacts of merely staying on our current carbon pollution emissions path — let alone looking at the plausible worst-case scenario (which is typically the basis for risk-reducing public policy, such as military spending).

Partly it’s because, until recently, climate scientists had naively expected the world to act with a modicum of sanity and avoid at all costs catastrophic warming of 7°F let alone the unimaginable 10°F (or higher) warming we are headed toward. Partly it’s because, as a recent paper explained, “climate scientists are biased toward overly cautious estimates, erring on the side of less rather than more alarming predictions.”

On top of the overly cautious nature of most climate scientists, we have the overly cautious nature of the IPCC. As the New York Times explained when the IPCC released the Working Group 1 report last fall:

The I.P.C.C. is far from alarmist — on the contrary, it is a highly conservative organization,” said Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany, whose papers on sea level were among those that got discarded. “That is not a problem as long as the users of the I.P.C.C. reports are well aware of this. The conservatism is built into its consensus structure, which tends to produce a lowest common denominator on which a large number of scientists can agree.”

That’s why the latest report is full of these sorts of bombshells couched in euphemism and buried deep in the text:

By 2100 for the high-emission scenario RCP8.5, the combination of high temperature and humidity in some areas for parts of the year is projected to compromise normal human activities, including growing food or working outdoors.

Yes, “compromise.” A clearer word would be “obliterate.” And the “high-emission scenario RCP8.5″ — an atmospheric concentration of carbon dioxide of about 936 parts per million — is in fact where we are headed by 2100 or soon thereafter on our current do-little path.

Bottom line: We are at risk of making large parts of the planet’s currently arable and populated land virtually uninhabitable for much of the year — and irreversibly so for hundreds of years.

THE RISK OF CREATING MORE FAILED STATES

Here are two important conclusions from the report that the IPCC strangely puts 13 pages apart from each other:

  1. Violent conflict increases vulnerability to climate change. Large-scale violent conflict harms assets that facilitate adaptation, including infrastructure, institutions, natural resources, social capital, and livelihood opportunities.
  2. Climate change can indirectly increase risks of violent conflicts in the form of civil war and inter-group violence by amplifying well-documented drivers of these conflicts such as poverty and economic shocks. Multiple lines of evidence relate climate variability to these forms of conflict.

Separately, they are both worrisome. But together, they are catastrophic. Climate change makes violent conflict more likely — and violent conflict makes a country more vulnerable to climate change. So climate change appears poised to help create many more of the most dangerous situations on Earth: failed states. Syria may be turning into an early example.

THE HIGH COST OF INACTION

The IPCC’s discussion of economic costs is equally muddled:

“… the incomplete estimates of global annual economic losses for additional temperature increases of ~2°C are between 0.2 and 2.0% of income. Losses are more likely than not to be greater, rather than smaller, than this range…. Losses accelerate with greater warming, but few quantitative estimates have been completed for additional warming around 3°C or above.”

It would have been nice if the IPCC had mentioned at this point that keeping additional temperature increases to ~2°C requires very aggressive efforts to slash carbon pollution starting now. As it is, the deniers, confusionists, and easily confused can (incorrectly) assert that this first sentence means global economic losses from climate change will be low. Again, that’s only if we act now.

As Climate Science Watch noted Saturday, “Other estimates suggest the high impacts on global GDP with warming of 4ºC (For example the Stern Review found impacts of 5-20% of global GDP).”

The costs of even higher warming, which, again, would be nothing more than business as usual, rise exponentially. Indeed, we’ve known for years that traditional climate cost-benefit analyses are “unusually misleading” — as Harvard economist Martin Weitzman warned colleagues, “we may be deluding ourselves and others.” Again, that’s because the IPCC is basically a best case analysis — while it largely ignores the business-as-usual case and completely ignores the worst case.

Remember, earlier this month, during the press call for the vastly better written climate report from the American Association for the Advancement of Science, a leading expert on risk analysis explained, “You really do have to think about worst-case scenarios when you are thinking about risk management. When it’s a risk management problem, thinking about worst-case scenarios is not alarmist — it’s just part of the job. And those worst-case scenarios are part of what drives the price.”

So where are we now? The first IPCC report last fall revealed we are as certain that humans are dramatically changing the planet’s climate as we are that smoking causes cancer. It found the best estimate is that humans are responsible for all of the warming we have suffered since 1950. It warned that on the continued do-little path, we are facing total warming from preindustrial levels by 2100 headed toward 4°C (7°F), with much more rapid sea level rise than previously reported, and the prospects of large-scale collapse of the permafrost, with resultant release of massive amounts of greenhouse gases.

Now, “the IPCC’s new report should leave the world in no doubt about the scale and immediacy of the threat to human survival, health, and wellbeing,” which in turn shows the need for “radical and transformative change” in our energy system, as the British Medical Journal editorialized.

Every few years, the world’s leading climate scientists and governments identify the ever-worsening symptoms. They give us the same diagnosis, but with ever-growing certainty. And they lay out an ever-grimmer prognosis if we keep ignoring their straightforward and relatively inexpensive treatment. Will we act on the science in time?

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