The role of land surface processes in local, regional
and global weather and climate

Abstract

The land surface is involved in interfacial fluxes of momentum, heat, moisture and other trace gases into and from the atmopshere. Diurnal, seasonal and longer term changes in this fluxes result in changes in the overlying atmosphere.

My talk describes the significant changes on local weather and climate due to deliberate and inadvertant human changes in the land surface, which necessarily alters these fluxes. The effect on long term temperature records is presented as one example of the consequences of these land use changes. The effect on mesoscale and regional weather and climate due to land use change are then illustrated, including significant effects on precipitation. The scaling upwards to the global scale through teleconnections from the effect of regional land use change is then described. It is shown, for example, that tropical deforestation, through teleconnections, changes weather and climate patterns thousands of kilometers away in the higher latitudes.

The consequences of this added climate forcing on climate policy are discussed. When included with other recently recognized human-caused climate forcings, such as the effect of aerosols on precipitation processes, a conclusion of the talk is that climate prediction is much more complex than implied by international assessments such as the IPCC. Indeed, the IPCC perspective underestimates the potential threats that human alteration of the climate system poses. An alternative paradigm, focusing on vulnerability, is presented as a more robust procedure to reduce societal threats from the human intervention in the climate system.

Suggested readings:

• Chase, T.N., R.A. Pielke, T.G.F. Kittel, R.R. Nemani, and S.W. Running, 2000: Simulated impacts of historical land cover changes on global climate in northern winter. Climate Dynamics, 16, 93-105. link
• Pielke Sr., R.A., G. Marland, R.A. Betts, T.N. Chase, J.L. Eastman, J.O. Niles, D. Niyogi, and S. Running, 2002: The influence of land-use change and landscape dynamics on the climate system- relevance to climate change policy beyond the radiative effect of greenhouse gases. Phil. Trans. A. Special Theme Issue, 360, 1705-1719. link
• Pielke Sr., R.A., 2001: Influence of the spatial distribution of vegetation and soils on the prediction of cumulus convective rainfall. Rev. Geophys., 39, 151-177. link
• Pielke, R.A. Sr. and L. Bravo de Guenni, Eds., 2004: How to evaluate the vulnerability in changing environmental conditions. Chapter E In: Vegetation, Water, Humans and the Climate: A New Perspective on an Interactive System. P. Kabat et al., Eds., Global Change - The IGBP Series, Springer, 566 pp.