Even 450 ppm Could Soon Be Out of Reach, PWC Warns

When the most traditional consultancies in the world note that the world's economies are emitting far more carbon dioxide than even the most optimistic models suggest is safe, that the trajectories we’re on have a terminus marked “oven,” it’s a real alarm.

Like many alarms, it means, wake up.

Who? Where? PriceWaterhouseCoopers LLP (PWC), which recently released a study suggesting that “we have been eating into the finite carbon emissions budget more quickly than we should, leaving us with a carbon debt.”

The study goes on to note that according to its calculations and modeling, the world has been reducing its “carbon intensity,” the carbon emitted per unit of GDP, at just .8 percent per year between 2000 and 2008.

It would be slight progress, except for a couple of things. The first is that world GDP was generally growing through those years, so that even though carbon emitted per unit of GDP went down slightly, total carbon emissions rose, year-on-year, on the whole. The second is that in order to reach the goals the PWC study stipulates, the world would have needed to “decarbonize” at the rate of two percent per annum throughout the 2000-2008 period. That means that according to this study, we’re already seriously off-target.

"For 2000-8, the cumulative global budget overshoot, or ‘carbon debt’, is estimated at around 13 GtC02 (roughly equivalent to the annual carbon emissions of China and the U.S. combined in 2008)," PWC notes. "Global carbon emissions in 2008 were already around 10% above levels implied by these estimated annual budgets. Even the EU is 7% off track."

This is bad news. The study suggests that we need to change course, sharply: to a 3.5 percent annualized reduction in carbon intensity between 2008 and 2020, merely to get back on a safe path, and so that we can stabilize global CO2 parts-per-million at around 450, which the study claims is the minimum needed in order to “stand a fair chance” of limiting average global changes in temperature to 2 degrees Celsius. If the world is not on course by 2020, there will be real problems. If stasis continues, it “could require rates of decarbonization over the longer term that are incompatible with growth, and put the 450 ppm goal out of reach.”

In order to move forward, the world must, first, budget carbon allocations. First, that involves a roof on total gigatons of CO2: 1,300. Second, that means distributing that CO2 budget among various countries or groups of countries. The study suggests that China should get to emit 28 percent of that CO2, the United States 16 percent, India 9 percent, the EU 10 percent, with the rest divided up among the rest of the countries of the world.

The idea of budgeting the world’s carbon emissions is the idea behind Kyoto and Copenhagen — there needs to be a treaty that says how much CO2 countries can spew into the atmosphere.

The first, and most important thing to note, is that according to the PWC models, the world is failing to meet the basic target that would reasonably ensure a safe planet for humans to live on. The second thing is that the PWC models are predicated on a 450 ppm standard. Rajendra Pachauri, head of the IPCC, has said that 450 ppm would bring with it disaster:

"The Maldive Islands, which are barely a meter above sea level, most of those islands, extensive areas of Bangladesh, a country of 160 million people, and there are other regions, including parts of the U.S., that will be completely devastated. And therefore even the 2-degree limit that we’re talking about, which corresponds to say about 450 parts per million, is pretty bad news."

Recognizing that these are unacceptable outcomes, British economist Nicholas Stern has endorsed a 350 ppm standard. NASA climate expert James Hansen suggests that a reasonable target is 300-350 ppm. 450 ppm is just too high.