WP6: Regional and Global Climate Effects

 

Coordinated by W. Collins (MetO) and F. Giorgii (ICTP)

 

MEGAPOLI Partners involved: DMI, MPIC, ICTP, MetO, UHel, CUNI

Summary of progress toward objectives

Following the overall WP6 objective - to quantify the effects of megacities on climate from the regional to the global scale using coupled and uncoupled global and regional chemistry-climate models and by analyzing observation data - during the 1st year the following progress has been made toward specific objectives. For the 1st specific objective the focus is on running of an "annihilation" scenario (i.e. without any emissions for grids occupied by a megacity) and this includes preliminary model development. It is assumed that regional models will use boundary conditions of meteorology and composition from existing global runs; and emissions for year of 2005 for the regional and global runs will be taken from WP1 and IMAGE scenario RCP2.6 for the CMIP5 project, respectively. Following the 2nd objective a simple analytical model was used to calculate the global temperature increase due to megacity emissions of the long-lived greenhouse gases, GHG (CO2, N2O, CH2, HCFC). Some progress has been made towards the methodology of use satellite and ground-based measurements in order to assess the TOA radiative fluxes, surface aerosol radiative forcing and AOD induced by megacities (O6.3). For the 4th specific objective the 6-hourly climate data will be provided from a Met Office HadGEM2 simulation using a CMIP5 scenario.

 

Summary details for each relevant WP deliverables, milestones, and tasks

Task 6.1: Regional and global radiative forcing and climate effects from constituent changes (lead by MetO, ICTP)

This task is linked with specific objective O6.1 (To implement the fields of radiative forcing agents into global and regional climate models in order to quantify the TOA and surface radiative forcing (direct and indirect) and related climate effects from scenarios). For this task "annihilation" scenarios have been run, i.e.  with emissions set to zero for grids occupied by a megacity. These runs are the same as used to provide the composition change in WP5. Aerosol forcings are diagnosed from double radiation calls, the ozone and methane forcings are diagnosed from changes in the global budgets. The regional models use boundary conditions of meteorology and composition from existing global runs. The emissions for the regional models are taken from WP1. The emissions for the global models are taken from the IMAGE scenario RCP2.6 for the CMIP5 project. Emission year is 2005.
Generally, the contribution of megacities to global pollutant emissions is on the order of 2% to 5% of the total global annual anthropogenic emission flux. The impact of megacity pollutants is assessed via a direct radiative forcing from ozone, methane and aerosols. Megacity pollutants are found to contribute a radiative forcing of +6.30.4 mW/m2 from an increase in the ozone burden due to pollutant photochemical oxidation. The change in methane lifetime and consequently the change in the CH4 abundance in the atmosphere contributes a forcing of -1.00.5mW/m2. The aerosol forcing from megacity pollutants amounts to -15.30.6mW/m2 in the short-wave spectrum and +2.00.1 mW/m2 in the long-wave spectrum (Figure 6.1). The combined effect of all of these individual terms is a slightly negative forcing, that is a cooling, of -8.01.6 mW/m2 of the climate at present-day conditions (Table 6.1).
 
 
(a)                                                                                                                (b)
Figure 6.1: Global distribution of  - (a) short-wave, SW all-sky and (b) long-wave,
LW clear sky - top-of-atmosphere (TOA) radiative forcing due to aerosols from megacities /Forcing is denoted in W/m2/.
 
Species DRF mW/m2 mW/m2
    HadGEM2 MATCH-MPIC
ΔOzone-DRF total TOA +6.30.4 +9.9
ΔMethane-DRF total TOA -1.00.5 -3.1
ΔAerosol-DRF [SW clear-sky TOA] [-40.40.3] [  ]
  SW all-sky TOA  -15.30.6
  LW clear-sky TOA +2.00.1
Total DRF    -8.01.6 -6.2
 
Table 6.1: Current best estimate of the present-day annual global mean direct radiative forcing (mW/m2) due to pollutant emissions from megacities as computed with the Met Office Hadley Centre Earth System Model HadGEM2 and the MATCH-MPIC chemistry-transport model from MPI-Chemistry Mainz.

 

         

Task 6.2: Radiative forcing and climate effects from long-lived greenhouse-gases, GHG (lead by MetO) 

This task is linked with specific objective O6.2 (To calculate the effect of long-lived GHG such as CO2, N2O, CH4, HCFC - megacity emissions on climate using simple algorithms) and it  was completed in year 1 (in advance of schedule). A simple analytical model was used to calculate the global temperature increase due to megacity emissions of the long-lived GHG. The emissions were taken from the EDGAR 4.0 inventory. HCFC emissions were not included as they were not available. A report is available as WP6 deliverable (D6.1 - Global radiative forcing from megacity emissions of long-lived greenhouse gases). Megacities are found to contribute around 12% of the anthropogenic emissions of the carbon dioxide and lesser fractions (due to their more distributed emissions) of methane and nitrous oxide. There is a wide variation in the emissions attributed to the different megacities, and little correlation between the emissions of the three gases (Figure 6.2). The climate impacts from megacity greenhouse gas emissions are calculated in terms of surface temperature change using a simple analytical climate model. For a step change in emissions, megacities contribute a warming of over 0.2K after 100 years (Figure 6.3). Most of this is due to carbon dioxide emissions. The other two gases methane and nitrous oxide contribute about 12% of the 100 year temperature change. Megacity emissions of nitrous oxide have only a very small impact on climate.

Figure 6.2: Emissions from 34 megacities for the year 2005 according to the Edgar 4.0 database. Emissions of CO2 are in Pg/yr, CH4 and N2O are in Tg/yr, although values for CH4 have been divided by 10 to keep them on the same scale.
 
 
(a)                                                                                                      (b)
Figure 6.3: Evolution of the concentration changes (a) and temperature changes (b) resulting from a step change of megacity emissions. 

Task 6.3: Measurements (lead by UHel)

This task is linked to specific objective 6.3 (To use satellite and ground-based measurements in order to assess the TOA radiative fluxes, surface aerosol radiative forcing and AOD induced by megacities) and some progress has been made towards the methodology of these measurements. This task is underway.

 

Task 6.4: Climate change meteorology/ Climate feedback (lead by MetO, MPIC)

This task is linked to specific objective 6.4 (To provide future-climate meteorological fields) and for this task the 6-hourly climate data will be provided from a Met Office HadGEM2 simulation using a CMIP5 scenario. The climate scenarios are successfully running on the Met Office computer. When complete, work will be needed to package the output appropriately and make it available.

Milestone 6.1: Determination of tradeoffs between different model setups and optimal configurations for further simulations of regional and global climate changes due to megacities (lead: MetO, ICTP)
has been achieved. The sub-meeting (about 10 persons) was held at the 1st Annual MEGAPOLI meeting in Copenhagen, DK. After introduction of participants and current status of their research teams contributions for the MEGAPOLI the following topics were discussed: comparison of passive tracer dispersion from several models; radiative forcing simulations (including coupled vs. uncoupled); comparison of forcing to observations; boundary conditions for regional models; and meteo and chemistry data.

Deliverable D6.1: Global radiative forcing from megacity emissions of long-lived greenhouse gases (lead by MetO)

in a form of the MEGAPOLI report (available for public) was completed on a schedule - Collins W.J. (2009): Global radiative forcing from megacity emissions of long-lived greenhouse gases. Deliverable D6.1, MEGAPOLI Scientific Report 09-01, MEGAPOLI-01-REP-2009-10, 17p., http://megapoli.dmi.dk/publ/MEGAPOLI_sr09-01.pdf

Deliverable D6.2: Determinate of radiative forcing from megacity emissions on global and regional scales (lead by MetO)

in a form of the MEGAPOLI report is being completed on schedule - Gerd A. Folberth, Steve Rumbold, William J. Collins, Tim (2010): Determination of Radiative Forcing from Megacity Emissions on the Global Scale. Deliverable D6.2, MEGAPOLI Scientific Report 10-08, MEGAPOLI-11-REP-2010-03, 19p., http://megapoli.dmi.dk/publ/MEGAPOLI_sr10-08.pdf.

Deliverable D6.3: Comparison of Measured and Modeled Radiative Effects (lead by UHel)
in a form of the MEGAPOLI report is being completed on schedule - Hannukainen M., de Leeuw G., Collins W.J. (2011): Comparison of Measured and Modeled Radiative Effects. Deliverable D6.3, MEGAPOLI Scientific Report 11-13, MEGAPOLI-39-REP-2011-08, 22p, ISBN: 978-87-92731-17-3, http://megapoli.dmi.dk/publ/MEGAPOLI_sr11-13.pdf

Deliverable D6.4:
Comparison of Coupled and Uncoupled Models (lead by MetO)
in a form of the MEGAPOLI report is being completed on schedule - Rumbold S.T., W.J. Collins, G.A. Folberth (2010): Comparison of Coupled and Uncoupled Models. Deliverable D6.4, MEGAPOLI Scientific Report 10-20, MEGAPOLI-23-REP-2010-11, 15p, http://megapoli.dmi.dk/publ/MEGAPOLI_sr10-20.pdf

Deliverable D6.5: Meteorological Fields for Present and Future Climate Conditions (lead by MPIC)
in a form of the MEGAPOLI report is being completed on schedule - Lawrence M. G., Butler T. M., Collins W., Folberth G., Zakey A., Giorgi F. (2010): Meteorological Fields for Present and Future Climate Conditions. Deliverable D6.5, MEGAPOLI  Technical Note 10-14, MEGAPOLI-17-REP-2010-09, 9p., http://megapoli.dmi.dk/publ/MEGAPOLI_sr10-14.pdf

Deliverable D6.6: Regional and Global Climate Changes due to Megacities using Coupled and Uncoupled Models. (lead by UK MetO)
in a form of the MEGAPOLI report is being completed on schedule - Folberth G.A., S. Rumbold, W.J. Collins, T. Butler (2011):  Regional and Global Climate Changes due to Megacities using Coupled and Uncoupled Models. Deliverable D6.6, MEGAPOLI Scientific Report 11-07, MEGAPOLI-33-REP-2011-06, 18p., http://megapoli.dmi.dk/publ/MEGAPOLI_sr11-07.pdf

Significant results: Methodologies and scientific achievements related to WP including partners' contributions

 MetO contribution (Climate forcing of LLGHGs, Global model development)
MetO developed an analytical climate model to quantify the impacts of CO2, CH4 and N2O emissions from megacities on global surface temperatures. This model used simple expressions to simulate the carbon cycle and the removal of methane and nitrous oxide. The model was driven by 2005 emissions from EDGAR 4.0 at 1 x 1 deg masked with a 1 x 1 deg megacity map from MPIC. The results show that if megacities maintain their 2005 emissions, this will lead to a 225 mK global temperature rise over the next 100 years. 200 mK of this is driven by the CO2 emissions with the rest from methane and nitrous oxide. MetO has also improved the chemistry in the HadGEM2 climate model by adding higher hydrocarbon chemistry and biogenic emissions of isoprene and terpenes. These are important for the formation of secondary organic aerosol which has a climate impact. The relative importance of isoprene, terpenes and anthropogenic VOCs for SOA production has been determined. The method of diagnosing radiative forcing changes through calling the model radiation scheme twice (double call method) has been implemented and is being used to generate results for deliverable D6.2. Transient climate change runs have started using the HadGEM2 climate model, they have progressed from 1860 to 1990 and are expected to reach 2100 in time for delivery of D6.5 in month 24.

 ICTP contribution (Regional model development)

ICTP determined a regional model domain to develop chemistry-climate feedback over European mega cities; and developed an emission pre-processor for RegCM3 (which take into accounts consider all of the available global emission inventories). ICTP also coupled an on-line biogenic VOC emissions module (MEGAN) to the land surface model of RegCM, enabling an interactive treatment of natural emissions and climate; as well as coupled a suite of gas phase chemical mechanisms to RegCM3 and evaluated the model over preliminary simulations in Europe.  Based on comparisons with an observational network of ozone data, the results indicate that the gas-phase schemes accurately simulate ozone, an important greenhouse gas. In RegCM, several gas-phase mechanisms running from comprehensive to condensed gas-phase were coupled. It is planned to use the condensed gas-phase mechanism for the long climate-chemistry simulation, while the comprehensive one will be used for the case-studies.  Several chemical mechanisms and several chemical solvers within the framework of the ICTP-RegCM were tested.  These included the following: 1) updated GEOS-CHEM, using Sanford Sillman box model code; 2) updated GEOS-CHEM (GEOS_KPP) using KPP to produce the code; 3) CBMZ (CBMZ_KPP) using KPP to produce the code; and 4) RACM (RACM_KPP) using KPP to produce the code.

MPIC Contribution (Global model development)

MPIC has developed the 1 x 1 deg megacity mask which is used in deliverables  D6.1 and D6.2.  In addition, the EMAC global chemistry-climate model will be used to simulate the climate impacts of megacity emissions.

DMI Contribution (Regional modelling)

DMI team is involved only in the Task 6.1 with the on-line coupled Enviro-HIRLAM model for specific case studies to understand better the mechanisms of non-linear feedback chains/loops, e.g. aerosols - radiation/clouds/PBL - chemical composition. This work considers short-term runs with 15 km resolution and focuses on further improvements of 2-way feedback mechanisms (first of all the 1st and 2nd aerosol indirect effects) in the model. Sensitivity studies for these two aerosol indirect effects on meteorological and chemical transport processes were performed for the domain with the Paris metropolitan region in the centre (see more details in WP4).

UHel Contribution (Measurements)

Progress has been made on Task 6.3 by the UHel team.

CUNI Contribution (Regional modelling)

CUNI has continued tests of methodology of interactive coupling in RegCM-CAMx couple and made plans for the domain definition covering all MEGAPOLI targeted regions in high resolution.

 

Discussion and conclusion
The WP6 delivered its first deliverable (D6.1) to schedule. The model development during the 1st year ensured that the groups were ready to start the simulations required for the next deliverable (D6.2 - Determination of radiative forcing from megacity emissions on global and regional scales) which is being delivered on schedule.

 

List of WP6 reports, publications, presentations

Collins W.J. (2009): Global radiative forcing from megacity emissions of long-lived greenhouse gases. Deliverable 6.1, MEGAPOLI Scientific Report 09-01, 17p, MEGAPOLI-01-REP-2009-10, ISBN: 978-87-992924-1-7, http://megapoli.dmi.dk/publ/MEGAPOLI_sr09-01.pdf

Korsholm U. (2009): Integrated modeling of aerosol indirect effects - develoment and application of a chemical weather model. PhD thesis University of Copenhagen, Niels Bohr Institute and DMI, Research Department;  http://www.dmi.dk/dmi/sr09-01.pdf

Gerd A. Folberth, Steve Rumbold, William J. Collins, Tim (2010): Determination of Radiative Forcing from Megacity Emissions on the Global Scale. Deliverable D6.2, MEGAPOLI Scien-tific Report 10-08, MEGAPOLI-11-REP-2010-03, 19p, http://megapoli.dmi.dk/publ/MEGAPOLI_sr10-08.pdf

Other reports and relevant publications are covered under WP5.

 


FP7 EC MEGAPOLI, 2008-2011