Eleven billion

A report published by Science called "World population stabilization unlikely this century" gives an 80 percent chance for 9.6 to 12.3 billion people by 2100.  This contrasts with previous projections that had population stabilizing or peaking at around 9 billion.  Naturally, this complicates scenarios for carbon dioxide emissions and for food production.

Update (October 28):  A study published in Proceedings of the National Academy of Sciences finds that various scenarios to reduce population have very little long-term impact.  This study projects a population of 10.4 billion by 2100.

Update (March 2, 2015):  The book Overdevelopment, Overpopulation, Overshoot looks at the impact of human population on the planet.

Update (August 11, 2015):  A United Nations analysis projects 11.2 billion people by 2100.

Update (July 14, 2019):  A reminder from Stephen Corry that growing populations (such as in Africa) in and of themselves aren't the biggest problem.

[I]f overpopulation is a problem because it strains the world’s resources, then the first and most efficient way to address it is not in Africa at all, it’s to reduce consumption in the North, which currently uses far more than its share of resources. Secondarily, if rates of population growth continue to fall when standards of living go up, then the easiest way of addressing that – inside Africa – would likely be to stop the massive resource outflow from the continent, and ensure more of its vast natural wealth remains with and starts fairly benefiting its natural owners.

In other words, to address “overpopulation,” the richer countries must do two things – consume less and stop stealing Africa’s resources. Both imply less for the Global North, and of course that’s the real problem with my simplified explanation.

Moral Imperative

Economics is one aspect of preventing catastrophic climate change, but there are arguments for the ethics as well.  David Roberts paraphrases the choice outlined by White House science advisor John Holdren:

We will respond to climate change with some mix of mitigation, adaptation, and suffering; all that remains to be determined is the mix.

Suffering is, of course, the "do nothing" path.  And Roberts makes the case that while mitigation efforts benefit the entire world, adaptation only helps in a local sense.

[F]or every day mitigation is delayed, the need for adaptation grows, most especially in places that will depend on the ongoing largesse of wealthier nations to pay for it. That’s not a recipe for egalitarian outcomes.

In an interview, Naomi Klein sees the need to combine morality with self-interest:

It’s immoral to allow countries to disappear beneath the waves when we have the power to prevent that from happening. It’s immoral to leave our children a world that is depleted of life and fraught with intense dangers that are also preventable. But I also make the argument that the things we need to do to stop catastrophic warming, they underline how interconnected we all are. If you look at relationships between the global north and the global south for instance, you can make moral arguments for why we should have more aid going to developing countries, and those are good arguments. But what climate does is it also adds a self-interest to that, where it’s not only that there needs to be more equity between the global north and the global south, it’s that unless we do this, them we can be pretty much guaranteed countries like China and India will continue developing on a path that is going to destabilize the global climate system. So unless we embrace principles of climate equity, we’re all cooked. It’s both moral and it’s self-interested.

Joe Romm discusses the essential points from her book, This Changes Everything: Capitalism vs The Climate.

Because we have ignored the increasingly urgent warnings and pleas for action from climate scientists for a quarter century now, the incremental or evolutionary paths to avert catastrophic global warming that we might have been able to take in the past are closed to us. 

Humanity faces a stark choice as a result: The end of civilization as we know it or the end of capitalism as we know it. 

Choosing “unregulated capitalism” over human civilization would be a “morally monstrous” choice — and so the winning message for the climate movement is a moral one.

Update (September 24):  Lindsay Abrams investigates how inequality impacts international adaptation efforts.

Update (September 29):  Robert Jensen reviews Klein's book.

Update (October 24, 2015):  Jonathan Chait thinks Klein is offering dangerous advice.

Climate and Economy

A report from the Global Commission on the Economy and Climate called The New Climate Economy concludes that preventing a 2 degree Celsius rise in global mean temperature can be accomplished with about $4 trillion or about 4.5 percent more than projected energy spending.

Update (September 19):  Paul Krugman criticizes both those on the right who only seem to be defending fossil fuel interests, and those on the left who say the end of growth is the only effective climate action.

Climate despair is all wrong. The idea that economic growth and climate action are incompatible may sound hardheaded and realistic, but it’s actually a fuzzy-minded misconception. If we ever get past the special interests and ideology that have blocked action to save the planet, we’ll find that it’s cheaper and easier than almost anyone imagines.

But just because the economics are favorable, doesn't mean the political will is there.  Inequality comes into it simply due to the imbalance of political influence.  A net cost might be near zero, but leaving fossil fuels in the ground is going to a huge loss for someone.

Update (September 20):  Rebecca Solnit says that "only collective action can save us now".

Update (September 21):  About 300,000 in New York City at the People's Climate March with as many as a couple thousand other events in 166 countries.

Update (October 13):  A study from World Resources Institute also points to many economic benefits from combating climate change.

Rising Carbon Dioxide

The World Meteorological Organization reports that the atmospheric carbon dioxide concentration averaged 396 parts per million in 2013.  The increase from 2012 to 2013 was the largest in nearly 30 years.  That seems to be due to not only greater emissions, but also reduced uptake in the biosphere.

Update (September 13):  More on the disruption of the carbon cycle.

Update (November 9, 2015):  The World Meteorological Organization says that the atmospheric carbon dioxide concentration averaged 397.7 parts per million in 2014.

Losing Ground

A report from the Economic Policy Institute shows how rising income inequality in the U.S. costs most people money.  Real income has been growing faster at the higher end, which leaves the typical middle-class household worse off than they would have been.

Update (September 4):  A survey by the Federal Reserve reports that the top 3 percent earn 30.5 percent of all income and hold 54.4 percent of the wealth in the U.S.

Update (September 6):  Wealth trends from the Federal Reserve survey.

Update (October 11, 2015):  The tie between productivity and compensation was broken 40 years ago.

Climate Synthesis

A draft of the Synthesis Report for AR5 from IPCC gives the bluntest language yet for where we are at:

Continued emission of greenhouse gases will cause further warming and long-lasting changes in all components of the climate system.

Without additional mitigation, and even with adaptation, warming by the end of the 21st century will lead to high to very high risk of severe, widespread, and irreversible impacts globally.

Update (August 27):  President Obama is seeking ways to reach a climate agreement without having to get the 67 votes needed in the U.S. Senate for a treaty.   It's pretty disgusting to have a political system where acting responsibly is practically impossible.

Update (August 29):  Republicans are already shouting "tyranny".

Update (November 2):  The Synthesis Report is now released.  According to U.N. Secretary-General Ban Ki-moon,

Science has spoken. There is no ambiguity in their message. Leaders must act. Time is not on our side.

Update (November 3):  More about the report.  Joe Romm calls it "incredibly alarming--while at the same time . . . terrifically hopeful."

Update (November 15):  Gideon Polya describes how AR5 downplays the seriousness of climate change.

Financial Priorities

Paul Buchheit uses six numbers to give a quick overview of who benefits in the U.S. economy:

$220 Billion: Teacher Salaries
$246 Billion: State and Local Pensions
$398 Billion: Safety Net
$863 Billion: Social Security
$2,200 Billion: Tax Avoidance
$5,000 Billion: Investment Wealth

In other words,

$8,600 for each of the  Safety Net recipients
$14,600 for each of the  Social Security recipients
$27,333 for each of the  Pension recipients
$54,740 for each of the  Teachers
$200,000 for each of the  Tax Break recipients among the richest 1%
$500,000 for each of the  Investment Income recipients among the richest 1%