Transcript Climate Change Impacts and Responses

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Climate Change:
Impacts and Responses
Topic 3:
Climate Change in the Distant Past:
Palaeoclimatology
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Topic outline
UN Photo credits: Evan Schneider, Mark Garten,
Martine Perret, Olga Lavrushko, Robert Clamp
1.
Introduction
2.
Types of climatic data for
analysing past climates
(direct and proxy
indicators)
3.
Past climate change:
evidence from proxy data
4.
Causes of climate change
in the past and the last
2,000 years
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Learning outcomes for this topic

Name sources of proxy climate
data

Describe the factors which have
caused shifts in climate in the
past

Describe the characteristics of
past climate change on Earth

Demonstrate an understanding
of climate change today within
the context of Earth’s prevailing
climate over the past two
thousand years

Debate the importance of recent
climate change relative to the
climate record of the distant past
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Section 1:
Introduction
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Outline:
Introduction
 Why study climate in the past?
 Climatic data
 Climate data from proxies
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Why study climate in the distant past?

To understand how
Earth’s climate can
change

To develop theories
to explain climate
changes

To build and test
climate models

To predict future
climate change
Fig SMP-01(a), IPCC AR5, 2013
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Climatic data
Image: NASA Earth
Observatory
Direct measurements:

From 1850s onwards – fairly reliable climate data recorded (from 1970s
onwards climate data also recorded by satellites)
Indirect measurements

Prior to 1850s we need to use proxy data
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Climate data from proxies
Proxy data are clues that enable scientists to
reconstruct past climates. They come from
indicators which record climatic variation.

Important indicators: Historical
records, natural phenomena, materials
and radioactive isotopes trapped in ice
or sediment.

Important sources: Tree rings, corals,
ice cores, lake and ocean sediments,
boreholes and mountain glaciers.

Challenges posed by proxy data: less
precise than instrumental
measurements, regionally specific
nature and uneven distribution.
Image: “Glaciers in Bhutan-Himalaya.”,
NASA Earth Observatory
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Section 2:
Types of proxy data
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Outline:
Types of proxy data

Tree rings

Corals

Ice cores

Sediments

Borehole measurements

Mountain glacial moraines
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The study of tree rings:
Dendrochronology
 Tree trunk crosssections display
patterns of tree
rings which relate to
annual growing
conditions
(temperature and
water availability)
and other events
such as floods and
fires
Pinus ponderosa trunk showing flood damage. Photo: Dr Henri D. Grissini-Meyer
 Tree rings can
provide climate
records going back
5,000 years for
some species
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Corals
Image: Owen Sherwood/www.noaa.gov

Annual growth rings

Record of several
hundred years

Tropical and subtropical range

Useful source of
information about
effects such as El Niño
events in the Pacific

Information about past
temperatures and levels
of ocean salinity
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Ice cores

Cylindrical samples of ice
mainly from Antarctica
and Greenland

Up to 800,000 years old

Temporal resolution is
depth dependent, with
annual/seasonal
resolution at shallower
depths

Ice formation and
inclusions such as air
bubbles

Sampling past
atmospheric
concentrations,
temperatures, wind,
volcanic eruptions etc...
Image: Lonnie Thompson/NOAA
Image: Mike Dunn, NOAA
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Sediments
(lakes, oceans and continental coastlines)
Image: “Sediment of the Yucatan Peninsular”, NASA Earth
Observatory

Lakes: annual

Oceans: multidecadal or century

Record goes back
millennia

Information about
past sea
temperatures,
salinity, acidity, ice
volumes, sea levels,
river outflows,
aridity and
vegetation
characteristics
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Borehole measurements
Reconstructed global ground temperature
estimate from borehole data over the past
five centuries, relative to present day.
Image created by Global Warming Art (after Huang & Pollack, 1998)

Temperature
profiles within
boreholes are
measured
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Greater depths
represent older
temperatures
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Decreasing
temporal
resolution
occurs with
increasing
depth
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Mountain glacial moraines
 Glaciers move through
landscapes leaving
characteristic rocky
debris known as
moraines.
 Moraines enable
scientists to measure the
maximum length of
glaciers and deduce
information about
temperature and
precipitation
 Such measurements can
be accurate to the
decade and records
going back millennia can
be constructed
Image: NASA Earth Observatory
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Time span of climatic records and
methods of dating
NOAA Palaeoclimatology program

Radiocarbon dating can be
useful for materials that are
up to about 50,000 years old
but dating can only be
accurate to a few percent of
the age of the material

Further back, Uranium
isotopes can be used but
resolution is lower still
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Uncertainty about dates
highlights the importance of
corroborating findings
between multiple proxies
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Past climate change:
Evidence from proxy data
Image created by Robert A. Rohde / Global Warming Art
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Section 3:
Past climates
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Outline:
Past climates
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Geologic time and palaeoclimatic events
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Pre-Quaternary

palaeocene/Eocene (PETM)

Mid-Pliocene

Quaternary

Holocene
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Geologic time and palaeoclimatic events
Quaternary
Pre-Quaternary
http://www.rocksinmyheadtoo.com/TimeLine.htm
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Geologic time and palaeoclimatic events
http://www.rocksinmyheadtoo.com/TimeLine.htm
65 million years: most of the useful proxy
data comes from this period
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Pre-Quaternary
IPCC 2007, Figure 6.1

CO₂ levels over the last 4
million years have varied in
line with continental
glaciation

CO₂ levels coincide with
temperatures and glaciation.

Over the last 65 million years,
deep ocean temperatures
fell overall

Antarctic and Northern
Hemisphere ice sheet
formation have occurred
within the last 35 million
years
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Palaeocene/Eocene (PETM)
IPCC 2007, figure 6.2

Abrupt warming of the
ocean by 5°C over a period
of 1,000 to 10,000 years 55
million years ago

Large carbon flux into the
atmosphere and ocean

This carbon was absorbed
by the ocean which made it
acidic and dissolved
seafloor carbonates. This is
evidenced by a break in
their presence in sediment
cores.
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Mid-Pliocene
Difference between mid-Pliocene and pre-industrial climate, as
modelled using PRISM2 palaeoenvironmental reconstructions and
the Hadley Centre atmospheric GCM.
 Most recent
period of
sustained
warmer
temperatures
 Greater
warming at
high latitudes
 Higher sea
levels and
changes to
ecosystem
distributions
http://www.bgs.ac.uk/research/climatechange/palaeo/computer_modelling.html
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Quaternary
Variations in a proxy for temperature (δD) and atmospheric
concentration of C02 (red), CH4 (blue) and N20 (green)
Figure 6.3, IPCC 2007
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Holocene
McMichael A J PNAS 2012;109:4730-4737
PNAS (National Academy of Science)
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Section 4:
Causes of climate change in the past
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Outline:
Causes of climate change in the past
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Abrupt climate change: Younger Dryas

Causes of past Ice Ages
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Palaeo-records in Africa
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The last 2,000 years
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Abrupt climate change: the Younger Dryas
 Best known example of
abrupt climate change
(occurring over decades)
 Sudden drop back to near
glacial conditions during
the warming transition
into the Holocene
 Probably caused by
massive influx of
meltwater from melting
ice sheets resulting in a
temporary reduction in
the thermohaline
circulation
Image: www.ncdc.noaa.gov
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Causes of past ice ages

Ice ages first hypothesised in
19th Century based on
evidence from glacial moraines
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Theories developed by James
Croll and then Milutin
Milankovitch linking ice ages to
orbital forcing

Feedback mechanisms amplify
this to ultimately affect Earth’s
climate over tens of thousands
of years.

Next ice age predicted to occur
in 30,000 years, but may not
operate as expected due to
impacts of anthropogenic
climate change
Milutin Milankovitch
IPCC 2007
James Croll
Artist’s impression of last
glacial maximum, Based on:
Crowley, Thomas J. (1995).
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Palaeo records in Africa
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Willis K J et al. Phil. Trans. R. Soc. B 2013;368:20120491
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The last two thousand years
Proxy-based
reconstructions of
Northern
Hemisphere
surface
temperature
variations over the
past two millennia
Image: Mann et
al, 2008
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Summary

Reconstructions of past climate change illustrate what is
possible within Earth’s climate system, and over what time
periods
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Throughout the climate record the close association of
atmospheric green house gas concentrations with temperature
is evident

Abrupt climate change has occurred before and a possible
cause is the influx of melt-water to the ocean from melting ice
sheets
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References
Alley, R.B., A.J. Gow, S.J. Johnsen, J. Kipfstuhl, D.A. Meese, and Th. Thorsteinsson. (1995). Comparison of deep ice cores.
Nature 373:393-394.
Folland, C.K., T.R. Karl, J.R. Christy, R.A. Clarke, G.V. Gruza, J. Jouzel, M.E. Mann, J. Oerlemans, M.J. Salinger and S.W. Wang
(2001). Observed Climate Variability and Change. In: Climate Change 2001: The Scientific Basis. Contribution of Working Group I
to the Third Assessment Report of the Intergovernmental Panel on Climate Change [Houghton, J.T., Y. Ding, D.J. Griggs, M.
Noguer, P.J. van der Linden, X. Dai, K. Maskell, and C.A. Johnson (eds.)]. Cambridge University Press, Cambridge, United Kingdom
and New York, NY, USA, 881pp
Huang, S.P., and H.N. Pollack, (1998). Global Borehole Temperature Database for Climate Reconstruction. IGBP PAGES/World
Data Center-A for Paleoclimatology Data Contribution Series #1998-044, NOAA/NGDC Paleoclimatology Program, Boulder, CO.
Huang, S, H Pollack & P-Y Shen (2000). Temperature trends over the past five centuries recenstructued from borehole
temperatures. Nature, vol 403(6771), 756–758
Jansen, E., J.Overpeck, K.R. Briffa, J.-C. Duplessy, F. Joos, V. Masson-Delmotte, D. Olago, B. Otto-Bliesner, W.R. Peltier, S.
Rahmstorm, R.Ramesh, D. Raynaud, D. Rind, O. Solomina, R. Vilalba and D. Zhang (2007). Palaeoclimate. In: Climate Change
2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental
Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]
Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA
McMichael, A.J. (2012). Insights from past millennia into climatic impacts on human health and survival. PNAS 2012 109 (13) 47304737; published ahead of print February 6, 2012,doi:10.1073/pnas.1120177109
Mann, M.E., Z. Zhang, M.K. Hughes, R.S. Bradley, S.K. Miller, S. Rutherford, and F. Ni (2008). Proxy-based reconstructions of
hemispheric and global surface temperature variations over the past two millennia. Proceedings of the National Academy of
Sciences Vol. 105, No. 36, pp. 13252-13257, September 9, 2008. doi:10.1073/pnas.0805721105
Riebeek, H. (2005). Paleoclimatology: Introduction. Available at: http://earthobservatory.nasa.gov/Features/Paleoclimatology/
Willis K. J., K. D. Bennett, S. L. Burrough, M. Macias-Fauria, and C. Tover (2013). Review article: Determining the response of
African biota to climate change: using the past to model the future. Phil. Trans. R. Soc. B 368:1625
Online resources:
http://www.ncdc.noaa.gov/data-access/paleoclimatology-data/datasets/climate-reconstruction
http://web.utk.edu/~grissino/
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Suggested reading
Dendrochronology (tree rings):
http://web.utk.edu/~grissino/resources.htm#educ
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End of Topic 3:
Climate Change in the Distant Past:
Palaeoclimatology
Next Topic:
Climate Change in the
Recent Past