**3.2 Effect of climate change**

The phrase climate change is used to describe a change in the climate, measured in terms of its statistical properties, e.g., the global mean surface temperature. In this context, climate is taken to mean the average weather. Climate can change over period of time ranging from months to thousands or millions of years. The classical time period is 30 years, as defined by the World Meteorological Organization. The climate change may be due to natural causes, e.g., changes in the sun's output, or due to human activities, e.g., changing the composition of the atmosphere. Any human-induced changes in climate will occur against the background of natural climatic variations.

The most general definition of *climate change* is a change in the statistical properties of the climate system when considered over long periods of time, regardless of cause, *whereas*  Global warming" refers to the change in the Earth's global average surface temperature. Measurements show a global temperature increase of 1.4 °F (0.78 °C) between the years 1900 and 2005. Global warming is closely associated with a broad spectrum of other climate changes, such as:

Global Trends of Fossil Fuel Reserves and Climate Change in the 21st Century 177

The most recent report IPCC projected that during the 21st century the global surface temperature is likely to rise a further1.1 to 2.9 °C (2 to 5.2 °F) for the lowest emissions

scenario used in the report and 2.4 to 6.4 °C (4.3 to 11.5 °F) for the highest

Fig. 6b. Projected Global Temperature Rise 1.1 to 6.4 °C during 21st century

Working Group I's contribution to the IPCC Fourth Assessment Report, published in 2007, concluded that warming of the climate system was "unequivocal" (*Solomon S, 2007a*). This was based on the consistency of evidence across a range of observed changes, including increases in global average air and ocean temperatures, widespread melting of snow and

Human activities have contributed to a number of the observed changes in climate (*Hegerl GC, et. al., 2007*). This contribution has principally been through the burning of fossil fuels, which has led to an increase in the concentration of GHGs in the atmosphere. This increase in GHG concentrations has caused a radiative forcing of the climate in the direction of warming. Human-induced forcing of the climate has likely to contributed to a number of observed changes, including sea level rise, changes in climate extremes (such as warm and

Human-induced warming could potentially lead to some impacts that are abrupt or irreversible. The probability of warming having unforeseen consequences increases with the

**3.2.2 Physical impacts of climate change** 

ice, and rising global average sea level(*Solomon S, 2007b*).

cold days), declines in Arctic sea ice extent, and to glacier retreat.

rate, magnitude, and duration of climate change.


#### **3.2.1 Impacts of climate change**

According to different levels of future global warming, impacts of climate has been used in the IPCC's Assessment Reports on climate change (*Schneider DH, et al., 2007*). The instrumental temperature record shows global warming of around 0.6 °C over the entire 20th century (*IPCC 2007d.1*). The future level of global warming is uncertain, but a wide range of estimates (projections) have been made (*Fisher, BS et al., 2007*). The IPCC's "SRES" scenarios have been frequently used to make projections of future climate change (*Karl, 2009*). Climate models using the six SRES "marker" scenarios suggest future warming of 1.1 to 6.4 °C by the end of the 21st century (above average global temperatures over the 1980 to 1999 time period) (*IPCC 2007d.3*). The projected rate of warming under these scenarios would very likely be without precedent during at least the last 10,000 years (*IPCC 2001-SPM*). The most recent warm period comparable to these projections was the mid-Pliocene, around 3 million years ago (*Stern N., 2008*). At that time, models suggest that mean global temperatures were about 2–3 °C warmer than pre-industrial temperatures (*Jansen E., et al., 2007*).

Fig. 6a. Global mean surface temperature difference from the average for 1880–2009

According to different levels of future global warming, impacts of climate has been used in the IPCC's Assessment Reports on climate change (*Schneider DH, et al., 2007*). The instrumental temperature record shows global warming of around 0.6 °C over the entire 20th century (*IPCC 2007d.1*). The future level of global warming is uncertain, but a wide range of estimates (projections) have been made (*Fisher, BS et al., 2007*). The IPCC's "SRES" scenarios have been frequently used to make projections of future climate change (*Karl, 2009*). Climate models using the six SRES "marker" scenarios suggest future warming of 1.1 to 6.4 °C by the end of the 21st century (above average global temperatures over the 1980 to 1999 time period) (*IPCC 2007d.3*). The projected rate of warming under these scenarios would very likely be without precedent during at least the last 10,000 years (*IPCC 2001-SPM*). The most recent warm period comparable to these projections was the mid-Pliocene, around 3 million years ago (*Stern N., 2008*). At that time, models suggest that mean global temperatures were about 2–3 °C warmer than pre-industrial

Fig. 6a. Global mean surface temperature difference from the average for 1880–2009

Increases in the frequency of intense rainfall,

 Decreases in snow cover and sea ice, More frequent and intense heat waves,

Widespread ocean acidification.

**3.2.1 Impacts of climate change** 

temperatures (*Jansen E., et al., 2007*).

Rising sea levels, and

The most recent report IPCC projected that during the 21st century the global surface temperature is likely to rise a further1.1 to 2.9 °C (2 to 5.2 °F) for the lowest emissions scenario used in the report and 2.4 to 6.4 °C (4.3 to 11.5 °F) for the highest

Fig. 6b. Projected Global Temperature Rise 1.1 to 6.4 °C during 21st century
