CACTI  Committee   Collaboration and Coordination  CACTI Workshop 2024  CACTI Workshop 2023

Composition Air quality Climate inTeractions Initiative (CACTI): Emissions to Response

Collaboration and Coordination


CACTI brings together the active and collaborative communities of RFMIP, AerChemMIP, and PDRMIP under a new initiative called CACTI (Composition Air quality Climate inTeractions Initiative: Emissions to Response). Previously, these communities came together as TriMIP. CACTI aims to follow on from the success of TriMIP. RFMIP aimed to characterize and assess ERF in CMIP6 models and determine errors when approximating accurate line-by-line radiative transfer with fast parameterizations used in climate models (Pincus et al., 2016). The main goals of AerChemMIP were to quantify the climate and air quality responses to aerosols and chemically reactive gases (Collins et al., 2017). The objective of PDRMIP was to understand global and regional responses of precipitation statistics to different forcing agents, and irradiance (Myhre et al., 2017). The three MIPs held joint meetings that were useful to inspire each other for scientific advancement of the field.


  • Wilcox, L. J., Allen, R. J., Samset, B. H., Bollasina, M. A., Griffiths, P. T., Keeble, J. M., Lund, M. T., Makkonen, R., Merikanto, J., O'Donnell, D., Paynter, D. J., Persad, G. G., Rumbold, S. T., Takemura, T., Tsigaridis, K., Undorf, S., and Westervelt, D. M.: The Regional Aerosol Model Intercomparison Project (RAMIP), Geosci. Model Dev. Discuss. [preprint],, in review, 2022.
  • Collins, W. J., Lamarque, J.-F., Schulz, M., Boucher, O., Eyring, V., Hegglin, M. I., Maycock, A., Myhre, G., Prather, M., Shindell, D., and Smith, S. J.: AerChemMIP: quantifying the effects of chemistry and aerosols in CMIP6, Geosci. Model Dev., 10, 585–607,, 2017.
  • Myhre, G., Forster, P. M., Samset, B. H., Hodnebrog, Ø., Sillmann, J., Aalbergsjø, S. G., Andrews, T., Boucher, O., Faluvegi, G., Fläschner, D., Iversen, T., Kasoar, M., Kharin, V., Kirkevåg, A., Lamarque, J.-F., Olivié, D., Richardson, T. B., Shindell, D., Shine, K. P., Stjern, C. W., Takemura, T., Voulgarakis, A., & Zwiers, F. (2017). PDRMIP: A Precipitation Driver and Response Model Intercomparison Project—Protocol and Preliminary Results, 98(6), 1185-1198, Bulletin of the American Meteorological Society,
  • Pincus, R., Forster, P. M., and Stevens, B.: The Radiative Forcing Model Intercomparison Project (RFMIP): experimental protocol for CMIP6, Geosci. Model Dev., 9, 3447–3460,, 2016.

New Collaborations

RAMIP joins the CACTI initiative. The first new MIP, RAMIP, from the former TriMIP community is already running. The aim of RAMIP is to quantify robust regional climate and air quality responses to regional emissions of anthropogenic aerosols (Wilcox et al., 2022). The experiments are designed to explore sensitivities to aerosol type and location using realistic, time-varying emission perturbations.


Our initiative adheres to scientific integrity, equal opportunities, and democratic leadership. Our values are for instance reflected by diversity in the scientific committee of CACTI, open email lists to inquire information on our activities and getting involved, hybrid meetings to allow participation from anywhere in the world, and open scientific discussions at our meetings for information transparency and the possibility for debates.

Tri-MIP-athlon meetings

Tri-MIP-athlon 2018, Reading, UK
Tri-MIP-athlon 2019, Princeton, USA
Tri-MIP-athlon 2021, online everywhere

MIP webpages