Archive for July, 2005

How Much Do We Have to Cut Carbon?

Tuesday, July 19th, 2005

We are 6.5 billion people emitting somewhat over 7.1 billion tonnes carbon, about 1.1 tonne per person. In the US, we emit about 5 3/4 tonnes per person.

The oceans are currently absorbing about 2 billion tonnes of carbon a year; the amount oceans can absorb will go down (slowly).

At the point that we want no more carbon to accumulate in the atmosphere, say 400 ppm, we must reduce carbon emissions to 2 billion tonnes total. With today’s population, that is 0.3 tonnes per person. If the population increases (duh), per capita emissions would need to be less. If our goal is 400 ppm, which we are on track to reach in about 10 years, then we need to limit the total amount of carbon above the 2 tonnes/year to about 50 billion tonnes. We can do that in ten years, or spread it out over a longer period of time. If we want to limit atmospheric carbon at a higher level, we will obviously have longer to achieve this goal. All plans that say we have decades to gradually adopt technology (and behavior change) assume that we will reach much higher levels of carbon. But in order to plateau, we must limit carbon (and other greenhouse gas) emissions to 2 billion tonnes carbon equivalent. (Of course, if we trigger accelerated climate change, eg, if the tundra begins to release its store of carbon which could dwarf our contribution, this analysis does not apply.)

Afterwards. carbon emissions would need to be slashed further to protect the oceans, because acidification is harming the oceans and will cause even greater harm. We are reducing the amount of food and protection (eg from tsunamis) that oceans can provide. See Ocean acidification due to increasing atmospheric carbon dioxide, the Royal Academy report.

A lot can be done with technology. A rapid shift to automobiles that get double today’s mileage, switching most light bulbs to compact fluorescent, increasing efficiency of air conditioners, massive subsidies of and use of solar power, possibly rapid addition of wind power (depending on what further studies show about wind power and climate change), tripling nuclear power or more, all this will help. In addition, the US and other rich countries can subsidize poorer countries in bypassing fossil fuels and going straight to solar, etc. If we pay the price of keeping other people’s emissions below their share, then that carbon is available to us.

Even with all of these technology changes, I suspect that behavioral changes will be needed above and beyond good insulation, Energy Star purchases, and buying very high mileage cars.

Someone wrote me, “when I read, ” the goal among scientists is…” I start counting my spoons. It sounds so priestly, so authoritative. “Scientists believe…” Which scientists, and why do they believe it?”

When I say scientists, I refer to consensus reports, eg, IPCC, or national academy reports, or what pretty much everyone says in every article on the subject in Science. Individuals may believe otherwise, but there is a pretty well developed system for the minority to get their ideas out and heard or rejected.

In order to know why scientists believe it, you may wish to look at IPCC reports.

The 400 ppm goal for atmospheric carbon comes from Meeting the Climate Challenge (google it and you’ll be able to get the pdf).

From a letter two of us wrote to Ministry and Oversight in Berkeley Friends Meeting, asking them to look at how Friends can begin to address environmental change:

The best understanding of the overwhelming number of those studying climatology and related subjects is that global warming is well underway because of human activity. We are creating too great a risk of abrupt changes in precipitation and temperature that will affect human life adversely. According to a report from the international climate change taskforce, exceeding a global average increase of more than 2 degrees Centigrade (2 C) will increase “the risks to human societies and ecosystems …significantly. It is likely, for example, that average temperature increases larger than this will entail substantial agricultural losses, greatly increased numbers of people at risk of water shortages, and widespread adverse health impacts. (Such an) increase …could also imperil a very high proportion of the world’s coral reefs and cause irreversible damage to important terrestrial ecosystems, including the Amazon rainforest…The risks of abrupt, accelerated, or runaway climate change also increase,” threatening, for example, “the loss of the West Antarctic and Greenland ice sheets (which, between them, could raise sea levels more than ten meters over the space of a few centuries), the shutdown of the thermohaline ocean circulation (and, with it, the Gulf Stream), and the transformation of the planet’s forests and soils from a net sink of carbon to a net source of carbon.” (Meeting the Climate Challenge: Recommendations of the International Climate Change Taskforce)

Basically, at 2 C there is too great a chance of abrupt, accelerated, or runaway climate change, and at 400 ppm, we have a 20% chance of passing 2 C. If my house were facing these odds of burning down, I’d probably do something. And my house burning down only affects my current possessions, not my access to food and water in the future.

We have lots of reasons to see scientists’ messages to us as being unrealistic. As someone who could benefit from a little weight loss, I can meet every reason you give, and go you one better. Alternatively, we can listen, and we can find ways to respond, both minor and major, both individually and collectively.

What do we tell all of the remaining generations of mankind — that scientists were unrealistic in their goals of reducing carbon so rapidly and sharply?