**3. Impact of climate change**

Due to prevailing nature of enhanced greenhouse effect in the atmosphere, the following effects have occurred at the global, regional and national levels.

Based on [3]; [4], there has been evidence of increase in global temperatures that has led to climate change at global, regional and national levels over the past 100 years. Increase in global temperatures experienced over the past century is as a result of accumulation of greenhouse gases in the atmosphere leading to global warming. Using complex climate models, the "Intergovernmental Panel on Climate Change" in their third assessment report has forecast that global mean surface temperature will rise by 1.40 C to 5.80 C by the end of 2100. Multiple datasets show essentially the same global warming trend over the past 100 years, with the steepest increase in warming in recent decades. The evidence of human-induced climate change goes beyond observed increases in average surface temperatures; it includes melting ice in the Arctic, melting glaciers around the world, increasing ocean temperatures, rising sea levels, acidification of the oceans due to excess carbon dioxide, changing precipitation patterns, and changing patterns of ecosystem and wildlife functions. Reduced agricultural productivity with the resultant food shortages has been experienced. Studies have shown that with higher concentrations of CO2, plants can grow bigger and faster. However, the effect of global warming may affect the atmospheric general circulation and thus altering the global precipi‐ tation pattern as well as changing the soil moisture contents over various continents.

knowledge in order to mitigate the severity of climate change and its impact on food security and livelihoods sustainability. Integration of agro-science and traditional agricultural systems

The expression of the term "climate change" according to many people means the alteration of the world's climate as a result of human activities through fossil fuel burning, clearing forests and other practices that increase the concentration of greenhouse gases (GHG) in the atmos‐ phere. This is in line with the official definition by the United Nations Framework Convention on Climate Change that states that climate change is the change that can be attributed "*directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods*" [1]. The Intergovern‐ mental Panel on Climate Change (IPCC) defines "climate change" as *"a change in the state of the climate that can be identified by changes in the mean and or the variability of its properties, and that persists for an extended period, typically decades or longer"* [2]. Climate change can be defined as a systematic change in the key dimensions of climate including average temperature and wind and rainfall patterns over a longer period of time. In recent usage, especially in the context of environmental policy, climate change usually refers to changes in modern climate. It may be qualified as anthropogenic climate change, more generally known as "global warming" or

Due to prevailing nature of enhanced greenhouse effect in the atmosphere, the following

Based on [3]; [4], there has been evidence of increase in global temperatures that has led to climate change at global, regional and national levels over the past 100 years. Increase in global temperatures experienced over the past century is as a result of accumulation of greenhouse gases in the atmosphere leading to global warming. Using complex climate models, the "Intergovernmental Panel on Climate Change" in their third assessment report has forecast

datasets show essentially the same global warming trend over the past 100 years, with the steepest increase in warming in recent decades. The evidence of human-induced climate change goes beyond observed increases in average surface temperatures; it includes melting ice in the Arctic, melting glaciers around the world, increasing ocean temperatures, rising sea levels, acidification of the oceans due to excess carbon dioxide, changing precipitation patterns, and changing patterns of ecosystem and wildlife functions. Reduced agricultural productivity

C to 5.80

C by the end of 2100. Multiple

effects have occurred at the global, regional and national levels.

that global mean surface temperature will rise by 1.40

is important if food security is to be sustained.

"anthropogenic global warming" (AGW).

**3. Impact of climate change**

**2. Global climate change**

236 Environmental Change and Sustainability


**Figure 1.** Depicts typical ravages of climate change in Kerio Valley, Kenya May 2012
