Earth System Science Dan Lunt Prof Paul Valdes

Earth System Science Dan Lunt, Prof. Paul Valdes, Prof. Tony Payne

Big Picture How do these systems work? What are the key drivers? How do the different parts interact? How do we measure and predict climate? What will happen in the near future? What has happened in the past?

Course aims and objectives • Introduce the study of the “Earth System” • Understand the processes important in influencing the Earth System • Understand the inter-connectivity of the major components of the Earth system • Develop an appreciation of the methods used for studying climate • Understand how and why we use climate models to inform our understanding of the climate system

Lecture series n Lecture 1: Introduction. Lecture 2: Future modelling and the IPCC. Lecture 3: Past Climate Changes Lecture 4: Geoengineering Lecture 5: Atmospheres Lecture 6: Energy balance modelling Lecture 7: Basics of General Circulation Modelling Lecture 8: Oceans Lecture 9: Ice sheet dynamics (1) Lecture 10: Ice sheet dynamics (2) n + practical sessions n n n n n

Assessment n Based on practicals n Write a brief report (in the style of a Nature paper) on your investigations with the climate model (e. g. a past or future simulation).

Text books n To help see the “overall” picture, you may wish to look at: Ø IPCC Working Group 1: Summary for Policymakers IPCC Working Group 1: Technical Summary Ø IPCC Working Group 1: Individual chapters (All available at http: //ipcc-wg 1. ucar. edu/wg 1 -report. html) Ø n Plus: n n n n Mc. Guffie K. and Henderson-Sellers A. , 2005. A Climate Modelling Primer. 3 rd Ed. Wiley. Barry R. G. and Chorley R. J , 2003. Atmosphere, weather and climate. 8 th Ed. Routledge. Bigg G. R. , 1996. The oceans and climate. 2 nd Ed. Cambridge University Press. Benn D. I. and Evans D. J. A. , 1998. Glaciers and glaciation. Hodder Arnold. Kump L. R. , Kasting J. F. , Crane R. G. , 2004. The Earth system: an introduction to Earth systems science. 2 nd Ed. Prentice Hall. Ruddiman W. F. , 2001. Earth’s climate : past and future. W. H. Freeman and Company. Holton, J. R. : An Introduction to Dynamic Meteorology. Academic Press. 4 th Ed. Peixoto & Oort “Physics of Climate”

Media

Government “Urgent action is needed to combat climate change” “Above all, climate change is the greatest challenge facing this generation. ” “Internationally, we will work for an ambitious, fair and legally binding climate change agreement”

Atmospheric CO 2

CO 2 emissions Oceans absorb approx. 25% of emissions, and land (plants) absorb a further 25% Leaving 50% of emissions to increase atmosphere concentration

The Greenhouse Effect

The Earth System Oldfield, p 4

General Circulation Models (GCMs)

History of GCMs 1990 1995 2001 2007

Surface Temperature: observations Surface Temperature: Had. CM 3 How good are GCMs? (1) temperature

Precipitation: observations Seaice: observations vs models Precipitation: Had. CM 3 How good are GCMs? (2) Precip and seaice

How good are GCMs? (3) El Nino

Radiative Forcing – anthropogenic component

Historical Forcing and response (century)

Historical Forcing and response (millenium)

Attribution (global)

Attribution (regional)

The future – climate sensitivity

Predicting the Future "Prediction is very difficult, especially if it's about the future. " --Nils Bohr, Nobel laureate in Physics "Those who have knowledge, don't predict. Those who predict, don't have knowledge. " --Lao Tzu, 6 th Century BC Chinese Poet "This is the first age that's ever paid much attention to the future, which is a little ironic since we may not have one. " --Arthur C. Clarke http: //www. met. rdg. ac. uk/cag/forecasting/quotes. html

SRES (special report on emissions scenarios) storylines (

SRES storylines Economic growth rapid Economic development regional - disparity Population peak 2050 Population continues rising Technological growth rapid Technological growth - slow, fragmented Capacity building A 1 F 1: fossil intensive Self reliance, heterogeneity A 1 T: non-fossil energy A 1 B: Balance Economic shift services/information Economic development intermediate Population peak 2050 Population continues rising slowly Technology -clean/efficient Technological growth diverse Global solutions to sustainability/equity Local and regional solutions to environment/equity No Additional climate initiatives

SRES storylines summary A 1 F 1 BAD B 1 GOOD From Jo House

SRES storylines summary Radiance calibrated lights obtained from night satellite imagery. Situation in 1995/1996 (bottom panel) and illustrative simulation for the SRES A 1 scenario's implied GDP growth for 2070 (top panel). IPCC SRES

SRES storylines in more detail IPCC TAR

SRES: Emissions Also include emissions scenarios for other greenhouse gases and aerosols. IPCC TAR synthesis report 2001

How to go from emissions to concentrations? Need to consider the components of the carbon cycle important on these timescales – ocean, land, and human pertubations. IPCC TAR

How to go from emissions to concentrations? However, we still don’t fully understand the Vostok CO 2 curve!! Petit et al, Nature, 399, 429 -436, 1999. From Andy Ridgwell

CO 2 concentration projections IPCC use relatively simple models to give CO 2 concentration scenarios…. . IPCC TAR

The IPCC Process - summary

Future Climate Predictions - global

Future Climate Predictions – regional (1) temperature

Future Climate Predictions – regional (2) Precipitation and cloud cover [stippling – at least 80% agree on sign of change]

Future Climate Predictions – regional (3) Ocean circulation

Summary Ø The atmospheric composition has changed over the last century. Ø The climatic consequences of these variations can be represented using numerical models. Ø These models do a relatively good job of the last century (millenium) compared to observations. Ø Climatic change over the last century is predominantly anthropogenic. Ø Future scenarios of atmospheric composition have been developed. Ø Some modelled consequences of these future changes are robust, others less so.