**WP2 Changes in atmospheric composition (CTM
simulations)**

Task 2.1 Emission perturbations (for CTM simulations)Task 2.2 CTM runsTask 2.3 Calculation of RF

Task 3.1 Perturbations of climate change agentsTask 3.2 Simulations for idealised forcing perturbationsTask 3.3 Simulations for realistic forcings

Task 4.1 Review of available metricsTask 4.2 Calculation of metricsTask 4.3 Scientific evaluation of metrics

Task 5.1 Development of refined metricsTask 5.2 Application of refined metricsTask 5.3 Scientific evaluation of metrics

Task 6.1 Political requirementsTask 6.2 Evaluation of existing metricsTask 6.3 Evaluation of refined metricsTask 6.4 Overall evaluation

**Task 2.1 Emission perturbations
(for CTM simulations)**

The main objective of Task 2.1 is

- to define a set of emission perturbations to be used in the chemistry transport models

The objectives of Task 2.2 are:

- to determine the change in tropospheric ozone and OH concentrations (and methane life-time) associated with selected perturbations of surface and free atmosphere emissions (e.g., from aircraft) of source gases (i.e., NOx, CO, NMHCs);
- to assess the dependence of changes in the O3 and OH concentrations on the location of the perturbation in the emissions (e.g., mid-latitudes versus tropics, surface versus upper troposphere);
- to calculate the future levels of ozone associated with additional emissions in ozone precursors including aircraft emissions, on the background of scenarios of future emissions (based on IS92 and the IPCC/SRES 2000)

The objectives of Task 2.3 are:

- to quantify the indirect RF associated with changes in ozone and CH4 concentrations;
- to calculate RF for various other perturbations

The objective of Task 3.1 is:

- to define sets of perturbations of climate change agents for GCM simulations.

The objective of Task 3.2 is:

- to perform GCM simulations for idealised perturbations designed in Task 3.1

The objective of Task 3.3 is

- to perform GCM simulations using realistic ozone perturbations using output from the CTMs described in Task 2.

**Task 4.1 Review of available metrics**

The objective of Task 4.1 is

- to review existing metrics of climate change.

**Task 4.2 Calculation of metrics**

The objective of Task 4.2 is

- to calculate the old metrics for the climate simulations of WP3.

**Task 4.3 Scientific evaluation of metrics**

The objective of Task 4.3 is

- to evaluate the existing metrics from the view point of natural sciences.

**Task 5.1 Development of refined metrics**

The objective of Task 5.1 is

- to develop refined metrics of climate change.

**Task 5.2 Application of refined metrics**

The objective of Task 5.2 is

- to calculate the refined metrics for the climate simulations of WP3.

**Task 5.3 Scientific evaluation of metrics**

The objective of Task 5.3 is

- to evaluate the refined metrics from the view point of natural sciences.

**Task 6.1 Political requirements**

The objective of Task 6.1 is

- to discuss and formulate requirements for climate metrics to be applicable by policy makers, both as a tool for decision making and as a tool for generating environmetally adequate solutions.

**Task 6.2 Evaluation of existing metrics**

The objectives of Task 6.2 are:

- to assess existing metrics according to requirements formulated in 6.1;
- to compare alternative existing metrics with respect to their capacity to serve these functions;
- to evaluate alternative existing metrics in terms of the extent to which they are associated with a trade-off between scientific accureaacy and political applicability and feeasibility;
- to evaluate existing metrics in terms of the extent to which they serve to include or exclude policy options.

**Task 6.3 Evaluation of refined metrics**

The objectives of Task 6.3 are:

- to assess refined metrics according to requirements formulated in 6.1;
- to compare alternative refined metrics (and existing metrics) with respect to their capacity to serve these functions;
- to evaluate alternative refined metrics in terms of the extent to which they are associated with a trade-off between scientific accuracy and political applicability and feasibility;
- to evaluate refined metrics in terms of the extent to which they serve to include ore exclude policy options.

The objective of Task 6.4 is

- to perform an overall evaluation of the metrics, both existing and refined (jointly from the view pints of natural sciences, economics and political science).

The objectives of the WP are:

- to publish results in scientific journals, in reports more accessible to policy makers, and on the internet;
- to publish selected model output on the internet.