Why I must speak out about climate change James Hansen
what do I know
that would cause me a reticent
Midwestern scientist to get myself
arrested in front of the White House
protesting and what would you do if you
knew what I know let’s start with how I
got to this point I was lucky to grow up
at a time when it was not difficult for
the child of a tenant farmer to make his
way to the State University and I was
really lucky to go to the University of
Iowa where I could study under professor
James Van Allen who built instruments
for the first u.s. satellites professor
Van Allen told me about observations of
Venus that there was intense microwave
radiation did it mean that Venus had an
ionosphere or was Venus extremely hot
the right answer confirmed by the Soviet
Venera spacecraft was that Venus was
very hot 900 degrees Fahrenheit and it
was kept hot by a thick carbon dioxide
atmosphere I was fortunate to join NASA
and successfully propose an experiment
to fly to Venus our instrument took this
image of the Vale of Venus which turned
out to be a smog of sulfuric acid but
while our instrument was being built I
became involved in calculations of the
greenhouse effect here on earth because
we realize that our atmospheric
composition was changing eventually I
resigned as principal investigator on
our Venus experiment because a planet
changing before our eyes is more
interesting and important if changes
will affect all humanity the greenhouse
effect had been well understood for more
than a century British physicist John
Tyndall in the 1850s made laboratory
measurements of the infrared radiation
which is heat
and he showed that gases such as co2
absorb heat thus acting like a blanket
warming Earth’s surface I worked with
other scientists to analyze earth
climate observations in 1981 we
published an article in science magazine
concluding that observed warming of 0.4
degrees Celsius in the prior century was
consistent with the greenhouse effect of
increasing co2 that earth would likely
warm in the 1980s and warming would
exceed the noise level of random weather
by the end of the century we also said
that the 21st century would cease
shifting climate zones creation of
drought prone regions in North America
and Asia erosion of ice sheets rising
sea levels and opening of the fabled
Northwest Passage all of these impacts
have since either happened or are now
well underway that paper was reported on
the front page of the New York Times and
led to me testifying to Congress in the
1980s testimony in which I emphasized
that global warming increases both
extremes of the Earth’s water cycle heat
waves and droughts on one hand directly
from the warming but also because a
warmer atmosphere holds more water vapor
with its latent energy rainfall will
become in more extreme events there will
be stronger storms and greater flooding
global warming hoopla became time
consuming and distracted me from doing
science
partly because I had complained that the
White House altered my testimony so I
decided to go back to strictly doing
science and leave the communication to
others by 15 years later evidence of
global warming was much stronger most of
the things mentioned in a 1981 paper
were facts I had the privilege to speak
twice to the president’s climate task
force but energy policies continued to
focus on finding more fossil
fuels by then we had two grandchildren
Sophie and Connor I decided that I did
not want them in the future to say oppa
understood what was happening but he
didn’t make it clear so I decided to
give a public talk criticizing the lack
of an appropriate energy policy I gave
the talk at the University of Iowa in
2004 and at the 2005 meeting of the
American Geophysical Union this led to
calls from the White House to NASA
headquarters and I was told that I could
not give any talks or speak with the
media without prior explicit approval by
NASA headquarters after I informed of
the New York Times about these
restrictions NASA was forced to end the
censorship but there were consequences I
had been using the first line of the
NASA mission statement to understand and
protect the home planet to justify my
talks soon the first line of the mission
statement was deleted never to appear
again over the next few years I was
drawn more and more into trying to
communicate the urgency of a change in
energy policies while still researching
the physics of climate change let me
describe the most important conclusion
from the physics first from Earth’s
energy balance and second from Earth’s
climate history adding co2 to the air is
like throwing another blanket on the bed
it reduces Earth’s heat radiation to
space so there’s a temporary energy
imbalance more energy is coming in than
going out until earth warms up enough to
again radiate to space as much energy as
it absorbs from the Sun so the key
quantity is Earth’s energy imbalance is
there more energy coming in than going
out if so more warming is in the
pipeline it will occur without adding
any more greenhouse gases now finally we
can measure Earth’s energy imbalance
precisely by measuring the
content in Earth’s heat reservoirs the
biggest reservoir the ocean was the
least well measured until more than 3000
Argo floats were distributed around the
world’s ocean these floats reveal that
the upper half of the ocean is gaining
heat at a substantial rate the deep
ocean is also gaining heat as smaller
rate and energy is going into the net
melting of ice all around the planet and
the land to depths of tens of meters is
also warming the total energy imbalance
now is about six tenths of a watt per
square meter that may not sound like
much but when added up over the whole
world its enormous it’s about 20 times
greater than the rate of energy use by
all of humanity it’s equivalent to
exploding
400,000 Hiroshima atomic bombs per day
365 days per year that’s how much extra
energy Earth is gaining each day this
imbalance if we want to stabilize
climate it means that we must reduce co2
from 391 ppm parts per million back to
350 ppm that is the change needed to
restore energy balance and prevent
further warming climate change deniers
argue that the Sun is the main cause of
climate change but the measured energy
imbalance occurred during the deepest
solar minimum in the record when the
sun’s energy reaching earth was least
yep there was more energy coming in than
going out this shows that the effect of
the sun’s variations on climate is
overwhelmed by the increasing greenhouse
gases mainly from burning fossil fuels
now consider Earth’s climate history
these curves for global temperature
atmospheric co2 and sea level were
derived from ocean cores in Antarctic
ice cores from ocean sediments and snow
flakes that piled up year after year
over 800,000 years forming a two-mile
thick ice sheet
as you see there is a high correlation
between temperature co2 and sea level
careful examination shows that the
temperature changes slightly lead the
co2 changes by a few centuries climate
change deniers like to use this fact to
confuse and trick the public by saying
look the temperature causes co2 to
change not vice-versa
but that leg is exactly what is expected
small changes in Earth’s orbit that
occur over tens to hundreds of thousands
of years alter the distribution of
sunlight on earth when there is more
sunlight at high latitudes in summer ice
sheets melt shrinking ice sheets make
the planet darker so it absorbs more
sunlight and becomes warmer a warmer
ocean releases co2 just as a warm
coca-cola does and more co2 causes more
warming so co2 methane and ice sheets
were feedbacks that amplified global
temperature change causing these ancient
climate oscillations to be huge
even though the climate change was
initiated by a very weak forcing the
important point is that these same
amplifying feedbacks will occur today
the physics does not change as earth
warms now because of extra co2 we put in
the atmosphere ice will melt and co2 and
methane will be released by warming
ocean and melting permafrost while we
can’t say exactly how fast these
amplifying feedbacks will occur it is
certain they will occur unless we stop
the warming there is evidence that
feedbacks are already beginning precise
measurements by grace the gravity
satellite revealed that both Greenland
and Antarctica are now losing mass
several hundred cubic kilometers per
year and the rate has accelerated since
the measurements began 9 years ago
methane is also beginning to escape from
the permafrost what sea level rise can
we look forward to the last time co2 was
390 ppm today’s value sea level was
higher by at least 15 meters 50 feet
where your city now would be underwater
most estimates are that this century we
will get at least one meter I think it
will be more if we keep burning fossil
fuels perhaps even five meters which is
18 feet this century or shortly
thereafter the important point is that
we will have started a process that is
out of humanity’s control ice sheets
would continue to disintegrate for
centuries there would be no stable
shoreline the economic consequences are
almost unthinkable hundreds of new
orleans like devastations around the
world what may be more reprehensible if
climate denial continues is
extermination of species the monarch
butterfly could be one of the twenty to
fifty percent of all species that the
Intergovernmental Panel on Climate
Change estimates will be ticketed for
extinction by the end of the century if
we stay on business as usual fossil fuel
use global warming is already affecting
people the texas-oklahoma Mexico
heatwave and drought last year Moscow
the year before and Europe in 2003 were
all exceptional events more than three
standard deviations outside the norm
fifty years ago such anomalies covered
only two to three tenths of 1% of the
land area in recent years because of
global warming they now cover about 10%
an increase by a factor of 25 to 50 so
we can say with a high degree of
confidence that the severe Texas and
Moscow heat waves were not natural they
were caused by global warming an
important impact if global
I mean continues will be on the
breadbasket of our nation in the world
the Midwest and Great Plains which are
expected to become prone to extreme
droughts worse than the Dust Bowl within
just a few decades if we let global
warming continue how did I get dragged
deeper and deeper into an attempt to
communicate giving talks in 10 countries
getting arrested burning up the vacation
time that I had accumulated over 30
years more grandchildren helped me along
Jake is a super positive enthusiastic
boy here at age two and a half years he
thinks he can protect his two and a half
day old little sister it would be
immoral to leave these young people with
the climate system spiraling out of
control
now the tragedy about climate change is
that we can solve it with a simple
honest approach of a gradually rising
carbon fee collected from fossil fuel
companies and distributed 100-percent
electronically every month to all legal
residents on a per capita basis with the
government not keeping one dime most
people would get more in the monthly
dividend than they pay in increased
prices this fee and dividend would
stimulate the economy and innovations
creating millions of jobs it is the
principal requirement for moving us
rapidly to a clean energy future several
top economists Sarco authors on this
proposition Jim to pestle of Republicans
for environmental protection describes
it thusly transparent market-based does
not enlarge government leaves energy
decisions to individual choices sounds
like a conservative climate plan but
instead of placing a rising fee on
carbon emissions to make fossil fuels
pay their true cost to society our
governments are forcing the public to
subsidize fossil
mewls by four hundred to five hundred
billion dollars per year worldwide thus
encouraging extraction of every fossil
fuel mountaintop removal long wall
mining fracking tar sands tar shale deep
ocean Arctic drilling this path if
continues guarantees that we will pass
tipping points leading to Ice Sheet
disintegration that will accelerate out
of control of future generations a large
fraction of species will be committed to
extinction an increasing intensity of
droughts and floods will severely impact
bread baskets of the world causing
massive famines and economic decline
imagine a giant asteroid on a direct
collision course with earth that is the
equivalent of what we face now yet we
differ
taking no action to divert the asteroid
even though the longer we wait the more
difficult and expensive it becomes if
we’d started in 2005 it would have
required emission reductions of 3% per
year to restore planetary energy balance
and stabilize climate this century if we
start next year it is 6 percent per year
if we wait 10 years it is 15 percent per
year
extremely difficult and expensive
perhaps impossible but we aren’t even
starting so now you know what I know
that is moving me to sound this alarm
clearly I haven’t got this message
across the science is clear I need your
help to communicate the gravity and the
urgency of this situation end its
solutions more effectively we owe it to
our children and grandchildren thank you
you