climate past future

8/3/2019 Climate Past Future

1/11

This is a graphical interpretation by David Spratt, Melbourne Climate Action Centre,

of aspects of recent paleo-climate research by Hansen et al, available in draft form at:

http://arxiv.org/abs/1105.1140

http://www.columbia.edu/~jeh1/mailings/2011/20110118_MilankovicPaper.pdf

http://www.columbia.edu/~jeh1/mailings/2011/20110514_PaleoAndImbalance.pdf

Version 1.5 of 6 June 2011

Eocene

peak

Our climate: past and future

Lessons from a warmer world

PETM natural

greenhouse event at55 million years ago.


2/11

Antarctic glaciation ~ 34 million years ago

Eocene

peak

Around 34 million years

ago, glaciation ofAntarctica at tail-end of

protracted upper Eocenecooling.

Relativetemperature


3/11

Around ~4.5 million years ago, northern hemisphere glaciation.

Associated with the rise of the Panama Cordillera which isolates

the Pacific from the Atlantic oceans and leads to intra-oceanic

circulation (Gyres) which introduces warm currents and moisture

to the North Atlantic resulting in increased snow fall and

formation of ice in Greenland, Laurentia and Fennoscandia.

Northern hemisphere glaciation ~ 4.5 million years ago

Eocene

peak

Relativetemperature


4/11

The last million yearsClimate swings

between ice ages

and warm

inter-glacial periodsover last million

years.CO2 between 180

and 300 parts permillion.

Carbon dioxide

and methane

over last

500,000 years

Relativetemperature


5/11

Peak of Holocene (over last 10,000 years up 1900AD)

The last 10,000 years the Holocene

PeakHolocene

temp.

Holocene: after the

last ice age, relativelystable temperatures

(+/0.5C) and sea-levels over last 10,000

years the period of

human civilisation

Relativetemperature


6/11


Global average temperature now ~0.6C above peak Holocene

Today temperature rises above the Holocene maximum

2010

CO2 level today (2011) is 391ppm but

thermal inertia (delay as ocean mass

warm) means temperature will increase

further.Temperatures have risen ~0.83C since

1900 and are now ~0.6C over peak

Holocene.

Relativetemperature


7/11



2C of warming: consequence of current level of greenhouse gases

2 degrees goodbye to Greenland ice sheet

+2C

When climate system

reaches equilibrium,present level of CO2 will

produce >2C of warmingwith feedbacks

Relativetemperature


8/11

Peak Holocene: over last 10,000 years up 1900AD



+2C

which is sufficient for large

parts of Greenland and West

Antarctic ice sheets to be lost,

leading to at least a 5-10 metresea-level rise over time

Goals to limit human-made

warming to 2rC.. are not sufficient

they are prescriptions for disaster

Dr James Hansen

Relativetemperature


9/11




4C of warming

4 degrees goodbye, goodbye

Best present emission reductioncommitments by all governments

(if implemented) will still lead to

4 degrees of warming by 2100

+4C

Relativetemperature


10/11




4C of warming

+4C

and likely loss overtime

of all ice sheets. No icesheets on planet = 70

metre sea-level rise overtime

amongst many devastating impacts.

Read more about 4 degrees hotter at

http://www.climateactioncentre.org/resources

Relativetemperature


11/11

the alternative scenario (Hansen et al 2011)

6% annual reduction in CO2 emissions starting 2013 plus 100

billion tonnes of reforestation between 2031 and 2080

reduces CO2 to below 350ppm by end of century.

Source: The Case for Young People and Nature: A Path to a Healthy, Natural, Prosperous Future (draft paper) by

James Hansen, Pushker Kharecha, Makiko Sato, Paul Epstein, Paul J. Hearty, Ove Hoegh- Guldberg, Camille

Parmesan, Stefan Rahmstorf, Johan Rockstrom, Eelco J.Rohling, Jeffrey Sachs, Peter Smith, Konrad Steffen, Karina

von Schuckmann, James C. Zachos

http://www.columbia.edu/~jeh1/mailings/2011/20110505_CaseForYoungPeople.pdf

climate past future

Documents