Using the climate of the past to predict the climate of the future

Danny McCarrollSwansea

‘Millennium’European climate of the last millennium

EU 6th Framework Integrated Project

41 partners

January 2006 – Dec 2010

Why were we funded?

•Reconstruct past climate•Improve predictions of future climate change

Climate Sensitivity

“change in global mean equilibrium temperature after a doubling of

atmospheric carbon dioxide”

1970s: 1.5 to 4.5˚C

IPCC 2007: 2.0 to 4.5˚C

“values substantially higher than 4.5˚C still cannot be excluded”

Likely range of mean global temperature increase by the end of the 21st Century

A1B: 1.7˚C to 4.4˚CA2: 2.0˚C to 5.4˚C

Temperature increases over land are likely to be roughly twice the global average and even larger in the north.

Change in temperature after CO2 doubling. Black lines: 2579 climateprediction.net runs. Red lines:127 30-year Hadley Centre simulations

Climateprediction.net

Ensembles of model runs predict many possible futures: which are most likely?

Note the uncertaintyIs not symmetrical

Hiro Yamazaki, Chris Huntingford, Myles Allen, Dave Frame

Simple one-box energy balance model to demonstrate the methodology

• model-data mismatch in temp. • likelihood of the choice of

calibration scaling coefficient• model-data mismatch for the

effective heat capacity of ocean in the instrumental period.

The overall likelihood of each model run is multiplication of:

Millennium will use a GCM, incorporating the geography of climate changes, and better uncertainty estimates for the palaeoclimate reconstructions

(Distributed via climateprediction.net)

Without palaeoclimateconstraint

With palaeoclimateconstraint

3 x CO2 stabilization scenario(similar to A1B until 2100)

“Millennium test set”

We do not need to fill every grid square

Different squares can contain different climate data

One square can contain several different climate variables

No need to average over time or space

1700 1750 1800 1850 1900 1950 2000

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JFMA Stockholm temperaturesReconstruction

Calibration: 1756-1841 Verification:1842-1892

R2 = 0.67 SE = 1.16DW = 2.06 Lin R = 0.16 (ns)

R2 = 0.60RE = 0.56CE = 0.56

RMSE = 1.13

Calendar Years

1700 1750 1800 1850 1900 1950 2000

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JFMA Uppsala temperaturesReconstruction

Verification:1842-1892

R2 = 0.66 R2 = 0.62RE = 0.61CE = 0.61

RMSE = 1.19

A

B

Verification:1722-1738R2 = 0.37RE = 0.63CE = -0.07

RMSE = 1.80

Verification:1739-1755R2 = 0.60RE = 0.59CE = 0.58

RMSE = 1.28

Winter temperature based on documentary evidence for dates of first and last ship to use Stockholm harbour

Lotta Leijonhufvud, Rob Wilson, Anders Moberg

The Holocene 2008, 18, 331-341

Extended back to AD 1500

Millennium special issue of Climatic Change

Documentary evidence (DE)

• DE sources interpreted to ordinal scale indices

• Indices express the temperature extremity of a given month (from -3 extremely cold to +3 extremely warm)

National T index series:• Germany (1500 – 1759)

• Switzerland (1500 – 1816)

• Czech Republic (1500 – 1854)

• Poland (1500 – 1700)

• Hungary (1500 – 1869)

• Low Countries (1500 – 2000)

CEU T index series1500 - 1854

used for cross- checking

Method of reconstruction

Calibration 1771 - 1816

Verification I. 1817 - 1854

Verification II. 1760 - 1770

Calibration 1771 - 1816

Linear regression model

CEU temperature reconstructions

Central Europe – monthly, seasonal and annual temperatures

Dobrovolný P, Moberg A, Brázdil R, Pfister C, Glaser R, Wilson R, van Engelen A, Limanówka D, Kiss A, Halíčková M, Macková J, Riemann D, Luterbacher J, Böhm R (2009) Monthly and seasonal temperature reconstructions for Central Europe derived from documentary evidence and instrumental records since AD 1500

Northern tree line summer temperatures from tree rings: dominated by Volcanic forcing

Sulphate loadings NH after Gao, and solar minima in green

Perturbed physics spin-up experiment. >25,000 variants of FAMOUS

Five solar forcing scenarios

Four volcanic forcing scenarios

148 model variants (perturbed physics)18 forcing combinations(Same aerosol and greenhouse gas forcing)

2664 Simulations AD800 to AD 2200Distributed in 200-year long work units

SRES A1B scenario until 2100 AD and held constant thereafter.

(They are not all ready yet, and lots of gaps!)

The Millennium experiment

20,000 to 30,000 FAMOUS model simulations have been running simultaneously on volunteer’s computers

Web-interface of the ClimatePrediction.net system

1 North Atlantic, May-Oct, AD 1000-2000, marine proxies2 Northern Fennoscandia, Jun-Aug, AD 1000-2004, tree-ring proxies3 Alpine region, Jun-Aug, AD 1053-2007, tree-ring and lake proxies4 Pyrenees, May-Sep, AD 1260-2005, tree-ring proxies5 Northern Fennoscandia, Apr-May, AD 1693-2010, river ice break records6 Southeastern Sweden, Jan-Apr, AD 1502-2008, harbour freezing records7 Central Europe, Dec-Feb, AD 1500-2007, documentary and early instrumental 8 Western Europe, Dec-Feb, AD 1659-2010, instrumental observations9 Northern Italy, Dec-Feb, AD 1789-2007, instrumental observations

We have a lot more!

Selected reconstructions

Selected reconstructions

Model ranking procedure

D2 = quadratic distance valueD2 value is computed for each of the nine proxy sitesD2 value computed using unforced simulationsT-value tests null hypothesis forced = unforcedLocal T-values summed and normalized

Used 30-year non-overlapping averages (33 points)Ranks plotted using colours, red (best 10) to blue.

This is a first attempt using incomplete data- suggestions welcome!

Hiro Yamazaki, Anders Moberg, Alistair Hind, Rolf Sundberg

Preliminary results

Concerns

•Model data still very incomplete•200-yr work units limit scope for internal variability•30-yr average may be too large for volcanic forcing•Should ranking exclude the ‘Greenhouse’ period? •Uncertainty in proxy reconstructions not yet included•Europe may be too small (internal > forced?)

•All suggestions warmly welcomed

Conclusions

•Method looks promising (but needs to be refined)•Likely range of future temperatures is constrained•Very high sensitivity models score poorly (good news)

•Bad news: All reasonable models under A1B predict •>2 degrees C rise by 2100 for mean annual T of Europe