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Appendix 35: The Earths Planetary Energy Imbalance

Dangerous human-made interference with climateExtracts from a paper by J.Hansen dated 22nd Dec 2005

The Intergovernmental Panel on Climate Change (IPCC 2001, http://www.grida.no )

considered a global warming of 2-3 degrees C likely to be dangerous. Hansen from the

NASA Goddard Institute for Space Studies (http://pubs.giss.nasa.gov) found that thedangerous level of global warming is closer to just 1 degree C. This is evidenced from the

Earths history of the last half million years in which global sea levels were around 5 m

higher than today and temperatures + 1 oC relative to today. At the end of the last ice age,around 15,000 years ago, ice volume change was rapid (Meltwater Pulse 1A;

http://www.mala.bc.ca/%7Eearles/mwp1a-mar02.htm ) when sea levels rose 20 m in 400

years or 1 m each 20 years.

The business-as-usual scenarios A2, A1B and A1FI with increasing CO2 and CH4 levels in

the atmosphere (down) will mean a warming of around 3 degrees oC far outside the rangewhich has existed on earth in millions of years. Hansen: If anthropogenic climatechange is several degrees Celsius, with equilibrium sea level rise25 10 m, a response time of centuries would provide littleconsolation to coastal dwellers, because they would be facedwith intermittent incursions associated with storms and withcontinually rebuilding above a transient sea level.

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Alternative scenariowith vulcanos

Scenario range which means a

different planet earth, outsideour experience. Ice meltingirreversible and out of control.
http://www.grida.no/http://pubs.giss.nasa.gov/http://www.mala.bc.ca/~earles/mwp1a-mar02.htmhttp://www.grida.no/http://pubs.giss.nasa.gov/http://www.mala.bc.ca/~earles/mwp1a-mar02.htm


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The alternative scenario target to keep added CO2 to ~ 80 ppmbetween 2000 and 2050, may already be beyond reach due tothe 2%/year growth of CO2 emissions in the past decade.Continued rapid growth of CO2 emissions for another decade,along with the infrastructure producing the emissions, wouldmake achievement of the alternative scenario impractical if notimpossible.

Given that wide-scale commercial use of technologies such aspower plants with CO2 sequestration is at least a decade or moreaway, this implies that strong near-term emphasis on energyefficiency and renewable energy is essential to achieve a

flattening of CO2 emissions. Potential energy savings fromimproved efficiency, even in developed countries, are sufficientto cover increased energy demand for the 1-2 decades needed tocommercialize improving energy technologies Source: http://pubs.giss.nasa.gov/docs/notyet/submitted_Hansen_etal_1.pdf

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This alternative scenario with reduced green

house gas emissions over the next decades is

still within reach but prompt action is needed

now, not later.
http://pubs.giss.nasa.gov/docs/notyet/submitted_Hansen_etal_1.pdfhttp://pubs.giss.nasa.gov/docs/notyet/submitted_Hansen_etal_1.pdf


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Green house gases are heating up (6) our already warm planet

earth which is now at the end of an interglacial period

(Holocene). Ice ages were around 6 degrees coolerthan at present. In the previous interglacial period(5) temperatures were 1 degree higher than todaywith sea levels 5-6 m above current levels.(The time scale for the last 150 years has been enlarged to show more detail)

Accumulating carbon dioxide

(1) and methane (2) in the

atmosphere from burningfossil fuels have now

exceeded all historic records

and constitute a human made

climate forcing which is muchgreater than the natural

forcing causing climate

swings. Another ice agecannot occur unless humans

become extinct.

James Hansen summarizes: "The Earth's temperature, with rapid globalwarming over the past 30 years, is now passing through the peak level ofthe Holocene, a period of relatively stable climate that has existed for morethan 10,000 years. Further warming of more than 1C will make the Earthwarmer than it has been in a million years. Business-as-usual scenarios,with fossil fuel CO2 emissions continuing to increase ~2%/year as in thepast decade, yield additional warming of 2 or 3C this century and implychanges that constitute practically a different planet."

The earths planetary energy imbalance

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2

1

3

4 56

Data from Antartic ice core


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http://pubs.giss.nasa.gov/docs/2005/2005_Hansen1.pdf

This large planetary energy imbalance hasno known precedent, greatly exceeding theglobal mean energy imbalance associatedwith changes of the Earths orbital elementsthat paced the natural building and decay of

ice sheets. James Hansen is director of the NASAGoddard Institute for Space Studies and a researcher atthe Columbia University Earth Institute.

The human-made planetary

energy imbalance (moreenergy absorbed fromsunlight than theenergy emitted tospace as thermalradiation) has increased

from 0.2 W/m2 in 1950 and isnow an incessant 1 W/m2which goes into warming the

ocean and melting ice.

The fraction of theenergy imbalance thatgoes into ice melting(5-10%) will increase asthe atmospherebecomes moister andtransports energy more

efficiently to the ice,and especially as icestreams accelerate andmore ice is rafted towarmer regions.Black carbon (BC) frompollution acceleratesmelting. An imbalanceof 1 W/m2 translates toan increase of globaltemperatures of o C.

Energy in Watt/m2

Incoming solarenergy

340

Reflectedenergy natural

-100

Reflectedenergy human

-1

Radiated heatnatural

-240

Radiated heathuman

2

Net balance +1

4
http://pubs.giss.nasa.gov/docs/2005/2005_Hansen1.pdfhttp://pubs.giss.nasa.gov/docs/2005/2005_Hansen1.pdf


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Carbon dioxide emissions increase 2% pa

What happens to our CO2

emissions?

20-35% soaked up by

oceans, making them acidic 5-20% taken up by

vegetation and soil

58% accumulates in the

atmosphere

The increasing annual

emissions result in higher CO2concentrations (down,left), year

after year. This cannot continue

for very much longer without

serious consequences.

CO2 concentrations: A curve with increasing slope

becomes visible.

Keeling found that atmospheric

CO2 decreases in the daytimeas plants assimilate CO2 and

increases at night. While plants

take one breath a day, the Earthtakes one breath a year.

Stabilization of atmosphericCO2 levels in the next few

years would require a reductionof annual fossil fuel emissions

by 60% - 80%

There can be no doubt the Earth

is becoming warmer.

In 1998, temperature hadjumped 2 standard deviations

from the previous trend line,

caused by the strongest El Ninoof the century.

Green house gases absorb theEarths infrared radiation and

reduce heat emissions to space.

This creates a temporaryplanetary energy imbalance.

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observed between thelast ice age 20,000 yearsago and today was 10 oCin Antarctica and 3 oCin the equatorial Pacific,

an average of 5 oC 1oC.

During that time period(recorded Egyptian history goes

back 5,000 years!) water levelsrose by 110 m. But during

Meltwater Pulse 1A, sea levels

rose by 1 m each 20 years!!

Sea levels (along with temperatures) were comparatively constant forthe last 8,000 years, one of the factors allowing civilisation to takehold. When ice is disintegrating, sea level rises can be fast, ashappened during the so-called Meltwater Pulse 1A event when sealevels rose by 20 m in 400 years or 1 m per 20 years.

Source : http://en.wikipedia.org/wiki/Image:Post-Glacial_Sea_Level.pngPaleoclimate Forcings

Total ice age climate forcingsIce sheets and vegetation 3.5 1 Watt/m2

CO2 + CH4 + N2O 2.6 0.5 Watt/ m2

Aerosols 0.5 1 Watt/ m2

Total 6.6 1.5 Watt/ m2

The climate sensitivity is measured in degree

temperature change per Watt/ m2 climate forcing.

With a total temperature change between ice ages and

interglacial periods of 5 oC we get:

Climate forcing is measured in

Watt per m2 of the Earthssurface. 1 Watt/m2 acting for

1000 years could melt enough

ice to raise sea levels by 100 m.

Under natural, paleoclimateforcings, the Earth is in

radiation balance within a

fraction of 1 Watt/m2.

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http://en.wikipedia.org/wiki/Image:Post-Glacial_Sea_Level.pnghttp://en.wikipedia.org/wiki/Image:Post-Glacial_Sea_Level.png


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5 oC / 6.6 Watt/ m2 = 0.75 0.25 oC per Watt/ m2

Climate Forcings in the industrial period

The burning of fossil fuels has introduced many new climate

forcings. Including natural forcings (changes in sun radiation andvolcanic activities) they amount to a total of 1.85 W/m2

Watt/m2

CO21.5

0.2

CH4,CFCs 1.2 0.3

O3 0.4 0.2

Blackcarbon

0.6 0.3

Reflectiveaerosols

-1.0 0.5

Forced

cloudchanges

-1.0 0.6

Land cover

change-0.15 0.2

Sun 0.3 0.2

Total 1.85

1880 2003 climate forcing 1.85 W/m2Observed 0.75 oC increase corresponds to 0.75 oC/climate sensitivity = 1 W/m2

Difference from time lag between forcing and temperature increase = 0.85 W/m2

More warming in the pipeline: 0.85 * 0.75 = 0.6 oC

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The above industrial climate

forcings have been put into a

climate simulation model. Thegraph shows the resulting net

radiation at the top of

atmosphere resulting fromdifferent assumptions

Greenland ice melting

http://news.nationalgeographic.com

Hurricane intensity in Gulf of Mexico increasing

Atmospheric CO2, CH4, and temperature for the past 400,000 yearsSource:http://www.columbia.edu/~jeh1/keeling_talk_and_slides.pdf

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http://news.nationalgeographic.com/http://www.columbia.edu/~jeh1/keeling_talk_and_slides.pdfhttp://www.columbia.edu/~jeh1/keeling_talk_and_slides.pdfhttp://news.nationalgeographic.com/http://www.columbia.edu/~jeh1/keeling_talk_and_slides.pdf


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Slideshow by James Hansen, NASA Goddard Institute for Space Studies

Burning of fossil fuels now endangers a sea level which was relatively stable for 8,000

years

Summary:

Is there still time to rescue our climate? Yes, but..

1. An alternative scenario in which green house gas emissions are being reduced canstabilize the Earths climate, but this strategy is currently not being pursued in the

required GHG reduction quantities and at the required speed2. 10 years of business as usual (more fossil burning infrastructure) and an

alternative scenario at a later stage will no longer be able to control a run-away

climate change in future3. Action is therefore needed now, not later. Green house gas reductions must be 60

80 % to ensure that temperature increases do not exceed 1 oC in this century

4. The public must understand these facts and put as much pressure on politicians asis needed to overcome vested interests of the fossil fuel industry

Facts:

(a) We are now in the Holocene, an interglacial period, which lasted for about 10,000

years with a comparatively stable climate and sea level. The preceding ice age, at

its peak 20,000 years ago, was around 5 oC cooler than now. Sea levels were 110m lower. The previous interglacial period was 1 oC warmer than today and sea

levels 5-6 m higher than at present.

(b) Green house gas emissions from burning fossil fuels since the industrialrevolution now result in heating up an already warm planet Earth. An increase in

surface temperatures of 0.75 oC since 1880 has already been measured. Due to the

time lag between green house gas emissions and surface temperatures, a further

0.6

o

C is unavoidably in the pipeline. A further warming of 2-3

o

C resulting frombusiness as usual would mean a different planet Earth outside our present and past

experience

(c) The processes controlling the Earths temperature, green house gasconcentrations, ice melting and sea level changes are highly complex and non-

linear. We do not fully understand the consequences of burning fossil fuels. This

life-experiment with our planet must stop before it gets out of control

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