Climate Change

Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.

Climate change will affect the basic elements of life for people around the world – access to water, food production, health, and the environment. Hundreds of millions of people could suffer hunger, water shortages and coastal flooding as the world warms." Stern Review 2006

Consensus amongst international climate change experts:

"Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely (greater than 90%) due to the observed increase in anthropogenic greenhouse gas concentrations." IPCC Report 2007

"Climate change will affect the basic elements of life for people around the world – access to water, food production, health, and the environment. Hundreds of millions of people could suffer hunger, water shortages and coastal flooding as the world warms." Stern Review 2006

Climate Change and the Greenhouse Effect

Climate change is caused by globally rising temperatures due to the emissions of man-made greenhouse gases (GHG). Since 1750 the Earth’s population has increased 10 fold; a sustainable way of living has been replaced by an intense exhaustion of natural resources. Advances in technology have led to an exponential increase in emissions of greenhouse gases since the onset of industrial revolution.

Greenhouse (=heat-trapping) gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and ozone (O3) amongst others. These gases have the ability to store heat from incoming solar radiation (Figure 1). In pre-industrial times these gases helped to maintain an appropriate temperature level which allowed plants and animals to thrive. Over the last 250 years levels of greenhouse gases were altered due to human activities such as burning of fossil fuels and land use change. Consequently, these gases have accumulated in the atmosphere where they now trap much more heat; hence the greenhouse effect.


Figure 1: The Greenhouse Gas Effect.

CO2 is the most important anthropogenic (man-made) greenhouse gas and the current level of atmospheric CO2 exceeds by far the natural range over the last 650,000 years (IPCC 2007). Globally, CO2 is largely produced by the transportation and electricity sector. Furthermore land use changes contribute to the rapid increase of anthropogenic CO2 in the atmosphere. Examples include the rapid expansion of agriculture and deforestation of carbon sequestering (=carbon storing) rain forest.

CH4 and N2O levels have risen 2.4 and 1.2 fold, respectively, from pre-industrial times to today. Sources are mostly agricultural activities; however, current inventories are still preliminary estimates (IPCC 2007).

What happens if we don’t take action?

Direct effects from temperature increase

Heat waves

The global average temperature has risen 13.7 °C to 14.4 °C (56.3°F to 57.9°F) over the last 150 years (IPCC 2007). As a consequence extreme heat waves occur more frequently in certain locations and pose a serious threat to people. Exposure to extreme heats can lead to heat exhaustion and heat stroke and it affects especially older people and young children and raises the mortality. Source: http://www.pewclimate.org/docUploads/Regional-Impacts-Midwest.pdf

Example: Chicago is projected to experience 25 percent more frequent heat waves and Los Angeles a four-to-eight-fold increase in heat wave days by the end of the century (IPCC, 2007).

http://www.noaanews.noaa.gov/stories2006/s2677.htm

In Ocala, FL, the average temperature was around 67°F between beginning of last century and it increased to an average temperature of 69°F between 1966 and 1995 (EPA, source:http://yosemite.epa.gov/OAR/globalwarming.nsf/UniqueKeyLookup/SHSU5BUKSV/$File/fl_impct.pdf

Indirect effects from temperature increase

Extreme weather events

Temperature shifts influence weather patterns and the occurrence of more extreme weather events is likely. Hurricanes can become more intense and more heavy rain precipitation can lead to devastating floods. These events are not evenly distributed across the globe, but some locations are more likely than others to notice extreme weather events.

Example: "Atlantic hurricane seasons since 1995 have been significantly more active, e.g. more hurricanes and more intense hurricanes, than the previous two decades." Quote from NOAA's hurricane page (http://hurricanes.noaa.gov)

"There has been a substantial global increase (nearly 100%) in the proportion of the most severe tropical cyclones (category 4 and 5 on the Saffir-Simpson scale), from the period from 1975 to 2004." (Webster et al. 2005; http://www.sciencemag.org/cgi/content/full/309/5742/1844)

Sea level rise An indirect result of the greenhouse phenomenon is sea level rise. Over half of the Earth’s population lives in coastal zones; they are directly affected by rising sea level (Figure 3). In the USA, coastal states like Florida who depend on tourism and other coastal activities will be facing huge economic losses from sea level change.

Example: In some locations sea level rise is already apparent while at other locations it less obvious which is in part due to lack of data (Figure 4).


Figure 3: Sea level projections for Florida with an estimated increase

in sea level of 2 meters (= 78 inches). Source: http://www.geo.arizona.edu/dgesl/research/other/climate_change_and_sea_level/sea_level_rise/sea_level_rise_old.htm#images


Figure 4: Sea level rise in Key West (a) and Miami Beach (b). Source: Monthly and Annual Mean Sea Level Station Files from the Permanent Service for Mean Sea Level (PSMSL) at the Proudman Oceanographic Laboratory

Agriculture

Rising temperatures and more extreme weather events will have adverse effects on agricultural activities and consequently food productions. Depending on the region farmers will have to face more frequent floods or droughts and will be exposed to limited water supply. Consequences are soil erosion from flooded farmland or increased soil evaporation rates during drought periods. Enhanced atmospheric CO2 levels will have a beneficial fertilizing effect on the crop production, however, it is widely believed that temperature and precipitation changes will outweigh these benefits (IPCC 2007).

Example: Freshwater supply can be at risk if saltwater infiltrates groundwater causing agricultural losses. While some regions may see an increase in food production other regions will see a decline. In Florida lower yields could be encountered with citrus, sugarcane and tomatos (Source: http://www.nrdc.org/globalWarming/nflorida.asp).

Water resources

In regions that are heavily populated, e.g. the coastal areas in South Florida, water resources are under a lot of pressure. Extreme weather events like hurricanes put floodplains at risk while longer drought periods limit the water supply. Furthermore, aquatic ecosystems are at risk due to man-made changes in estuary and wetland areas.

Water quality is directly affected by increasing temperatures as it contains less dissolved oxygen which alters the aquatic life. Less water also implies a reduced dilution of pollutants; this can however be offset by increased precipitation.

Example: Despite its high precipation rate, water evaporation in Florida exceeds the rain fall on an annual average.