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