# Presentation: 266474

## An Update on Progress and Plans in IPCC WG1

- Susan Solomon     Co-Chair, Working Group I of the Intergovernmental Panel on Climate Change (IPCC) and Senior Scientist, NOAA Aeronomy Laboratory

## Intergovernmental Panel on Climate Change (IPCC)

- Established in 1988 jointly by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP).
- International participation from over 150 countries.
- Assesses on a comprehensive, objective, open, and transparent basis the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change (WG1), its potential impacts (WG2), and options for mitigation and adaptation (WG3).
- This talk:  (1) IPCC's planning, structure, review process; (2) some key inputs including our climate sensitivity workshop and some illustrative developments in the literature; (3) Solomon's draft assessment rules

## IPCC (2001):  Houghton (UK)

- and Ding (China) co-chairs

- News you can use:  policy-relevant but not policy-prescriptive reviews of the state of scientific understanding.

## Consultation, Scoping, and Some Procedural Matters of the AR4

- Government suggestions on outline solicited (twice)
- Two scoping meetings:  Participation by 42 distinguished scientific experts (including chairs of World Climate Research Program and International Geosphere Biosphere Program) from 19 countries, with leadership by WG co-chairs.
- Outline formally approved by Govts in Nov, 2003
- Authors nominated by Govts, chosen by WG1 Bureau; 25% of WG1 authors have had their highest degree for less than 10 years and 75% of them were not authors of the TAR.   There are 35% more DC/EIT authors among them than in TAR.
- Technical Support Unit organizes meetings, collates comments, provides editorial support, etc.

## Preparation and Review of the WG1 AR4

- Each report is an assessment of the state of understanding based upon peer-reviewed published work.
- Informal ZOD prepared, comments sought from 6-12 outside experts for each chapter (Oct 2004 - Mar 2005).
- Formal first order draft (FOD) reviewed by about 600 reviewers worldwide (Sept 9-Nov 4, 2005).
- Formal second order draft (SOD) to be prepared by March, 2006, will be reviewed by many hundreds of experts worldwide and many governments.
- WG1 expects to receive many thousands of comments from the hundreds of reviewers (compare this to a typical scientific paper, normally reviewed by 2-3 experts).

## Comprehensive bibliography is achieved by the end of the process (many reviewer comments focus on ensuring that the authors consider the full range of available work).   Coverage is shaped by the review. 
The many comments reflect a diverse variety of views.   Balance in content is shaped by the review.  
Many comments focus on issues of scientific confidence and uncertainty.  Uncertainty issues are shaped by the review.
Review Editors ensure that comments are afforded appropriate consideration by the authors.   Comments are formally archived.
A scientific process is ensured by the fact that the comments and responses are open. 
The breadth of the author teams and the breadth and depth of the review is not achieved by any other process. Thus assessed findings in a final IPCC report are not the views of any individual scientist and reflect a far broader process.

- The many comments reflect a diverse variety of views.   Balance in content is shaped by the review.
- Many comments focus on issues of scientific confidence and uncertainty.  Uncertainty issues are shaped by the review.
- Review Editors ensure that comments are afforded appropriate consideration by the authors.   Comments are formally archived.
- A scientific process is ensured by the fact that the comments and responses are open.
- The breadth of the author teams and the breadth and depth of the review is not achieved by any other process. Thus assessed findings in a final IPCC report are not the views of any individual scientist and reflect a far broader process.

**Preparation and Review of the WG1 AR4**

## Observations

## AR4 WG1 Report Structure

**Introduction: How has the understanding of the scientific basis of climate change advanced since IPCC began?** *(Chap 1)**Describe context and reasons for changes in understanding*
**Radiative forcing and observations:**** ****Can humans affect the climate system?  What changes in climate have been observed?** *(Chaps 2,3,4,5)**Human and natural influences on climate, followed by**observed variability and trends: atmosphere, ice and frozen ground, oceans including sea level*
**Past and present climate change and couplings to biogeochemical cycles: How well do we understand human contributions to past and present climate change?**  *(Chaps 6,7,8,9)**Paleoclimate, roles of biogeochemical cycles and human effects upon them, evaluation of models, understanding and attributing observed changes*
**Future projections: How is climate projected to change in the future?** *(Chaps 10,11)**Projections of future climate change globally and regionally, on time scales from decades to centuries.*

## Paris, July 2004

- A running start on one of the key central issues for AR4, a broad one that brought together models, observations, etc.
- Climate sensitivity defined here as the equilibrium temperature change for CO2 doubling
- (1.5-4.5° in TAR...and SAR...and FAR)

## Bounding climate sensitivity using forcing and 20th century trends

- What limits the utility?  Uncertainty in aerosols.  But there are still limits that can be determined......

**Notes:**
Klimasensitivität kann durch Beobachtungen nicht eingeschränkt werden

## Parameter Perturbations:  Probing Model Space in a New Way

**Large Scale Cloud**
-  Ice fall speed
-  Critical relative humidity for formation
-  Cloud droplet to rain: conversion rate and threshold
-  Cloud fraction calculation

**Convection**
-  Entrainment rate
-  Intensity of mass flux
-  Shape of cloud (anvils)
-  Cloud water seen by radiation

**Radiation**
-  Ice particle size/shape
-   Sulphur cycle
-  Water vapour continuum absorption

**Boundary layer**
-  Turbulent mixing coefficients: stability-dependence, neutral mixing length
-  Roughness length over sea: Charnock constant, free convective value

**Dynamics**
-  Diffusion: order and e-folding time
-  Gravity wave drag: surface and trapped lee wave constants
-  Gravity wave drag start level

**Land surface processes**
-  Root depths
-  Forest roughness lengths
-  Surface-canopy coupling
-  CO2 dependence of stomatal conductance

**Sea ice**
-  Albedo dependence on temperature
-   Ocean-ice heat transfer

## In progress:  improved estimates of climate sensitivity range 

**Estimated probabilities for climate sensitivity**** **** **

- In progress:  improved estimates of climate sensitivity range

## Many Advances in RF and Response: Surface Energy Budget

- Surface energy budget issues have been illuminated in many recent papers
- Effects on temperature profile?
- Effects not just on temperature but also on precipitation?

** **

- Satellites can now distinguish many aerosol types (soot, sulfate, dust....) and sources.  The mix of aerosols and the direct forcing is better understood and quantified.
- Indirect effects, role of clouds are key.

- Dust

- Biomass burning

- Pollution

- (Figures from Kaufman et al, Science 2002)

- Radiative Forcing:  Spectacular information on aerosols and tropospheric chemistry from space

## Atmosphere and Surface

- Cold

- Hot

- Hot

- PDO?

- NAO?

***Atmosphere and Surface***
- Temperature....and much more

- Hot

## There are some problems illuminated in previous reports that will need to be re-assessed carefully.   A famous one is the difference between temperature trends at the ground and a little higher up.

- CCSP assessment; will be a help to IPCC

- (ground)

- (higher up)

- New information on key points - to be assessed

## The ocean temperatures may affect land temperatures and precipitation in many areas.   

- The ocean temperatures may affect land temperatures and precipitation in many areas.

- How do the warmth of today’s oceans influence climate around the world?

## Future Changes...Mean Precipitation?

*Groisman et al., J. Clim, 2005*

## More heavy precipitation and more droughts?

- More heavy precipitation _and_ more droughts?

-  Warmer world implies more evaporation - but soils will dry out as a result.   So dry regions in mid-continents will get drier unless storm tracks shift in a lucky way.
-  "wet get wetter, dry get drier"      - S. Manabe

-  Warmer world implies more evaporation - more water goes to the atmosphere where water is available on the ground (e.g., oceans).  The atmosphere therefore will contain more water vapor available to rain out.  And most places receive the majority of their moisture in heavy rain events, which draw moisture from a big area.

## Evidence for a changing cryosphere

## Oceans and sea level

**New global observations by satellite**

- Observed sea level rise.  Thermal expansion is likely to be a major factor.  Connect to *in-situ* ocean heat content and other data.    Integrate these findings in one chapter.

- [Figures from Cazenave and Nerem, 2004]

## Global mean surface air temperatures are rising

- Global ocean heat content is also increasing
- So the atmosphere did not get hotter at the expense of the ocean.
- Role of global energy budget change, radiative forcing due to increases in GHG; *Hansen et al., Science, 2005.*

## Probability Distributions

- Stott and Kettleborough,Nature, 2002

**Probability Distributions**

- Probability distributions can provide more specific information on commitment due to past emissions, versus scenarios, and clarify model results.

## Solomon’s (Draft) Rules of 

**Solomon’s (Draft) Rules of **
**Successful Assessment**

**The product must be designed (and proven) to be useful....for **_**both**_** the stakeholders and the science community that produces it **
** ****There must be a clear demarcation of roles and procedures between the stakeholder/Governments and the scientists who produce the report **** **

- 3) **The report must go through several staged and different rounds of careful review by a very broad range of experts and stakeholders.**
**4) Scientific judgment must be the guiding force and final arbiter in the content and in responses to the review process.   Authors must have “author”-ity.**
**5) The author teams must have adequate time.  Never rush an assessment.**

## 6) The assessment conclusions must be fully grounded in well-documented peer-reviewed literature. 

**7) Stakeholder inputs must be provided in open yet formal forums (e.g., the IPCC plenary).****8) Clear science leadership must be provided by the chairs and lead author team, who are internationally known and respected scientists.**

## Rules for an IPCC co-chair to live by:

**...****..force no consensus before its time.**
**...****...policy-relevant but not policy-prescriptive assessment can be achieved because the best science is always highly self-critical and highly objective.  Rely on the scientific culture and ethic (which works well when it operates objectively within its own standards) and communicate this clearly to authors, governments, and others.  We are here to seek understanding, and only understanding.**

## What’s next for IPCC (2007)?