Page 22 - Solar Power in Building Design The Engineer's Complete Design Resource

xx INTRODUCTION

emissions. Increased deforestation, landfills, large agricultural production, industrial
production, and mining also contribute a significant share of emissions. In 2000, the
United States produced about 25 percent of total global greenhouse gas emissions, the
largest contributing country in the world.
Estimating future emissions depends on demographics, economics, technological
policies, and institutional developments. Several emissions scenarios have been devel-
oped based on differing projections of these underlying factors. It is estimated that by
the year 2100, in the absence of emission-control policies, carbon dioxide concentra-
tions will be about 30 to 150 percent higher than today’s levels.
Increasing concentrations of greenhouse gases are expected to accelerate global cli-
mate change. Scientists expect that the average global surface temperatures could rise
an additional 1ºF to 4.5ºF within the next 50 years and 2.2ºF to 10ºF over the next cen-
tury, with significant regional variation. Records show that the 10 warmest years of the
twentieth century all occurred in the last 15 years of that century. The expected
impacts of this weather warming trend include the following:

Water resources. A warming-induced decrease in mountain snowpack storage
will increase winter stream flows (and flooding) and decrease summer flows. This
along with an increased evapotranspiration rate is likely to cause a decrease in water
deliveries.
Agriculture. The agricultural industry will be adversely affected by lower water
supplies and increased weather variability, including extreme heat and drought.

Forestry. An increase in summer heat and dryness is likely to result in forest fires,
an increase in insect populations, and disease.

Electric energy. Increased summer heat is likely to cause an increase in the
demand for electricity due to an increased reliance on air conditioning. Reduced
snowpack is likely to decrease the availability of hydroelectric supplies.
Regional air quality and human health. Higher temperatures may worsen existing
air quality problems, particularly if there is a greater reliance on fossil fuel gener-
ated electricity. Higher heat would also increase health risks for some segments of
the population.
Rising ocean levels. Thermal expansion of the ocean and glacial melting are likely
to cause a 0.5 to 1.5 m (2 to 4 ft) rise in ocean levels by 2100.
Natural habitat. Rising ocean levels and reduced summer river flow are likely to
reduce coastal and wetland habitats. These changes could also adversely affect spawn-
ing fish populations. A general increase in temperatures and accompanying increases
in summer dryness could also adversely affect wildland plant and animal species.

Scientists calculate that without considering feedback mechanisms a doubling of carbon
dioxide would lead to a global temperature increase of 1.2ºC (2.2ºF). But, the net effect
of positive and negative feedback patterns would cause substantially more warming
than would the change in greenhouse gases alone.