In the last two years, our scientific understanding of business-as-usual projections for global warming has changed dramatically (see “M.I.T. doubles its projection of global warming by 2100 to 5.1°C” and “Hadley Center projects 5-7°C warming by 2100“). Yet, much of the U.S. public — especially conservatives — remain in the dark about just how dire the situation is (see “Gallup poll shows catastrophic failure of media, conservatives still easily duped by deniers“).

Why? Because the U.S. media is largely ignoring the story. Case in point: Where was the coverage of the Copenhagen Climate Science Congress, attended by 2000 scientists, which concluded with this Key Message #1:

Recent observations confirm that, given high rates of observed emissions, the worst-case IPCC scenario trajectories (or even worse) are being realized. For many key parameters, the climate system is already moving beyond the patterns of natural variability within which our society and economy have developed and thrived. These parameters include global mean surface temperature, sea-level rise, ocean and ice sheet dynamics, ocean acidification, and extreme climatic events. There is a significant risk that many of the trends will accelerate, leading to an increasing risk of abrupt or irreversible climatic shifts.

What is the worst-case IPCC scenario trajectory? That would be A1F1 (the red dotted line in the figure below from figure SPM-3 of the 2001 Intergovernmental Panel on Climate Change, Synthesis Report):

The A1F1 scenario takes us to atmospheric concentrations of carbon dioxide of 1000 ppm in 2100 — otherwise known as the end of human civilization as we have known it. Actually it’s worse than that. The 2001 IPCC report largely failed to model amplifying carbon cycle feedbacks. The 2007 IPCC report, which began to consider such feedbacks, warns that even averaging 11 GtC (billion metric tons of carbon) a year this century could take us to 1000 ppm (see “Nature publishes my climate analysis and solution“). The A1F1 scenario averages well above 15 GtC a year through 2100 as you can see from the figure on the left.

Energy Daily (subs. req’d) notes of the U.S. media non-coverage of Copenhagen:

Ironically–given the Gallup finding that two in five Americans think the press is exaggerating climate change concerns–only a few of the major U.S. news outlets published accounts of the Copenhagen gathering, which received heavy coverage by news outlets in Europe and Asia.

Great point — though “ironically” isn’t the right word. There is nothing ironic about this. It is cause and effect. The right word is “tragically.”

Exceeding A1F1 probably means total planetary warming by 2100 compared to preindustrial levels of 5°C or more. I discuss the harsh impacts of such warming here.

West Coast Climate Equity notes:

Last time mean global temperatures reached 2 to 3 degrees Celsius above present levels, in the mid-Pliocene (3 million years ago), an event associated with CO2 levels of about 400 parts per million, polar regions were heated by near-8 degrees C and sea levels have risen by 25+/-12 meters relative to the present. This represents near-total melting of Greenland and west Antarctica ice sheets (Robinson et al., 2008: “Pliocene role in assessing future climate impacts” (http://pubs.giss.nasa.gov/ abstracts/ 2008/ Robinson_etal.html).

A rise of mean global temperatures above 4 or 5 degrees Celsius would shift the atmosphere to pre-glacial/interglacial conditions, which dominated the Earth from about 34 million years ago (end-Eocene) (Zachos et al., 2008) http://www.nature.com/ nature/ journal/ v451/ n7176/ full/ nature06588.html

That means ultimate sea level rise of 250 feet, with the best current projection being 5 feet by 2100 (see “Startling new sea level rise research: “Most likely” 0.8 to 2.0 meters by 2100“), rising thereafter 10 to 20 inches a decade (or more) for centuries. Good luck adapting to that, next 50 generations.

Key Message #5 from the Congress is:

Key Message 5: Inaction is Inexcusable

There is no excuse for inaction. We already have many tools and approaches — economic, technological, behavioural, management — to deal effectively with the climate change challenge. But they must be vigorously and widely implemented to achieve the societal transformation required to decarbonise economies. A wide range of benefits will flow from a concerted effort to alter our energy economy now, including sustainable energy job growth, reductions in the health and economic costs of climate change, and the restoration of ecosystems and revitalisation of ecosystem services.

What is inexcusable is US media coverage and the blinkered conservative strategy of scientific denial — what can only be described as a murder-suicide pact with the human race (see “Hill conservatives reject all 3 climate strategies and embrace Rush Limbaugh — what does that radicalism mean for Obama, progressives, and humanity?“).

Link to Joseph Romm's blog post: http://climateprogress.org/2009/03/17/media-copenhagen-global-warming-impacts-worst-case-ipcc