director of NASA's Goddard Institute for Space Studies in New York, is
one of the world's most famous climatologists. He testified at a 1988 U.S. Senate hearing
that the emission of carbon dioxide from burning fossil fuels was
already producing a greenhouse effect, and during the administration of
George W. Bush, political appointees tried to keep him from speaking out about global warming.
Hansen, 68, has become increasingly convinced that a climate crisis is
upon us, warning this summer that the climate system is racing toward
"tipping points" which, if passed, would lead to irreversible and
catastrophic effects. On the eve of the publication of his first book, Storms of My Grandchildren,
which he finished while recovering from treatment for prostate cancer
and which will be published in December, he spoke to me by phone. Later
in the week, I followed up to discuss the news of leaked e-mails from researchers who allegedly ignored evidence unfavorable to climate change. Excerpts:
Last week, someone leaked e-mails obtained by hacking into
the server at the Climate Research Unit at the University of East
Anglia. Activists who have long denied the reality of climate change
say they show that climatologists have engaged in a grand
conspiracy to manufacture a case that global warming is occurring due
to human activities. Do the
undermine the case for anthropogenic climate change?
No, they have no effect on the science. The evidence for human-made climate change is overwhelming.
Do the e-mails indicate any unethical efforts to hide data
that do not support the idea of anthropogenic global warming or to keep
contrary ideas out of the scientific literature and IPCC reports?
They indicate poor judgment in specific cases. First, the data
behind any analysis should be made publicly available. Second, rather
than trying so hard to prohibit publication of shoddy science, which is
impossible, it is better that reviews, such as by IPCC and the National
Academy of Sciences, summarize the full range of opinions and explain
clearly the basis of the scientific assessment. The "contrarians" or
"deniers" do not have a scientific leg to stand on. Their aim is to win
a public relations battle, or at least get a draw, which may be enough
to stymie the actions that are needed to stabilize climate.
How serious a setback would it be if no agreement on a
climate treaty is reached in Copenhagen, where 192 countries are meeting
starting Dec. 7?
It's not a setback at all if it allows a
careful reassessment of what is needed. The cap-and-trade scheme [that
the Copenhagen negotiations were working toward] is just not going to be
effective at controlling greenhouse emissions. Political leaders have
to realize that the fundamental problem is that fossil fuels are the
cheapest form of energy, so they will continue to be burned unless we
put a gradually increasing price on carbon emissions [through a carbon
tax]. That's a much better approach than national goals for emissions
reductions, which will probably not be met.
Policymakers who deny the threat of climate change cite the research of Richard Lindzen of MIT and other scientists, who question the link between carbon dioxide and global warming—as the last head of NASA, Michael Griffin, also did. As long as there remains this scientific dispute, why should policy makers act?
contrarians are not having much effect. None of the major countries are
denying the problem anymore, though in the U.S. these contrarians are
still widely heard, and when it comes to passing a bill in Congress they
may still be an obstacle.
In the 1980s scientists worried about a doubling of
pre-industrial levels of carbon dioxide, to 550 parts per million. Then
450 started to look like a problem. Now you and others say that 350 is
dangerous, and we’re already at 387. What did climatologists learn that caused them to lower the estimate of dangerous CO2 levels?
new information came from observations of how the system is responding
to 387ppm and to more detailed information on how earth responded in the
past to different atmospheric compositions. For instance, we see that
the ice sheets are not stable at 387ppm; the Greenland and Antarctic ice
sheets are losing mass even with current warming. The Greenland ice
sheet had been losing between 150 and 200 cubic kilometers a year in
2002, and now is losing almost 300 cubic kilometers a year. Antarctica
had been losing less than 100 cubic kilometers a year, and is now losing
more than 150, so it seems like we're heading into a period of much
more rapid ice sheet loss. Also, in the arctic we've lost 40 percent of
the sea ice in the warm season, and that will soon be 100 percent.
Mountain glaciers are retreating rapidly
and could be gone in 50 years. These are not model results but
observations: 387ppm is already too high, and 450ppm will be far worse.
Storms of My Grandchildren
, you describe climate tipping points. What are some and why are they so dangerous?
Things like methane hydrates on
the continental shelf and the tundra: as they warm up they release
their methane [which is a greenhouse gas], which we're already seeing in
the tundra and elsewhere. Tipping points are so dangerous because if
you pass them, the climate is out of humanity's control: if an ice sheet
disintegrates and starts to slide into the ocean there's nothing we can
do about that.
What caused you to move beyond research and become an outspoken advocate for addressing climate change?
realization that there was a gap between what had become clear
scientifically and what policymakers knew. Then, when I wrote papers and
gave talks on climate change, it became clear that the political system
just didn't want to react to this. Scientists have to help politicians
connect the dots.
George F. Will has argued that reducing U.S. carbon emissions 80
percent by 2050 would leave us with per capita emissions we last had in
the 1800s, implying we'd be back to a horse-and-buggy, pre-electricity
era. Is he right?
Not at all. We don't have to decrease our energy use, we just
have to decrease our carbon emissions. That's why you want to increase
the price of carbon, so let other technologies take over, like energy
efficiency and renewables. We'll be moving into a better world, not a
worse one, not to a horse-and-buggy world but to one with cleaner air
and water once we stop burning coal. (Article continued below...)
You are critical of the Kyoto climate treaty. Why?
Because it allows carbon offsets and uses cap-and-trade. Emissions from oil, gas, and coal have actually increased
under Kyoto. If we just set goals for emissions reductions and allow
people to miss them and to use offsets, we're not going to stabilize and
reduce greenhouse emissions at the rate needed.
Do we still have time to avert climate calamity, and if so what would it take?
We do, but just barely. If we phase out coal linearly by 2030, CO2
concentrations in the atmosphere will peak at 400 to 425 ppm, which is
low enough that it allows you to get back to 350, especially if there is
extensive reforestation of degraded areas. So a fundamental requirement
is to phase out the use of coal in 20 years, which means you have to
start now and not build any more coal-burning power plants: these have a
lifetime of decades, and once they're built utilities don't want to
retire them before their lifetime is up.
You write that energy efficiency and renewables won't be
enough to meet the energy needs of China and India in the next few
decades. So what do we
They will require nuclear power for
electricity. They are both moving in that direction, and we really
should help them. They have such polluted air and water that they'd love
to get off dirty fuels like coal. Of course, you also want to do energy
efficiency and renewables, but I think India and China will turn more
toward nuclear. I think the prospects for that are quite good, but we
have to get going now.
What do you think of the climate bills now before Congress?
They're disasters. We can't allow the polluters to write the
bill, but that's what happened. What's needed is putting a price on
carbon, not cap-and-trade.
What do you think of Obama's performance on this issue so far?
A lot of individual things have been good, like using EPA to apply pressure for improved vehicle mileage,
but I'm disappointed that he hasn't taken a leadership role. He's let
the politicians in Washington come up with these bills rather than
offering them some guidance. Climate change is analogous to Lincoln and
slavery or Churchill and Nazism: it's not the kind of thing where you
can compromise. He needs to have some understanding of this [climate]
problem himself, and not just listen to his advisers.
Are policies like Cash for Clunkers, or "cash for
caulkers" [home weatherizing], or green jobs initiatives useful or just
They're useful but costly. What you want to do is address
[climate change] in the most cost-effective way possible, which is to
put a price on carbon. For example, there's a program to let people fold
the cost of improving the energy of their home or of adding clean
energy [by installing solar panels or other forms of renewable energy]
into their monthly mortgage payment. You decrease your monthly energy
costs by more than the amount that gets added to your mortgage, since
you're averaging the cost over several years. This works best if you
have a rising price on carbon.
You write about the need to take to the streets and engage in civil resistance. Such as? Anything that draws attention to the fundamental problem. We just had this example of the student in Utah who upset the Bureau of Land Management
by bidding on oil and gas leases, without even intending to pay for
them, in order to stop energy companies from acquiring them and drilling on public lands.
You make it sound like now that you've written the book, you're going to go hole up in your lab. Really?
I wish I could. But when I started to speak out about climate
change in 2004, after 15 years of avoiding it, I saw that the problem is
not going to be solved easily. I'm afraid this is going to continue.