Global warming will impact life on Earth in
many ways, but the extent of the change is largely up to us
is the unusually rapid increase in Earth’s average surface temperature over the
past century primarily due to the greenhouse gases released as people burn
fossil fuels. The global average surface temperature rose 0.6 to 0.9 degrees
Celsius (1.1 to 1.6° F) between 1906 and 2005, and the rate of temperature increase has
nearly doubled in the last 50 years. Temperatures are certain to go up further.
Earth’s natural greenhouse effect
Earth’s temperature begins with the Sun. Roughly 30
percent of incoming sunlight is reflected back into space by bright surfaces
like clouds and ice. Of the remaining 70 percent, most is absorbed by the land
and ocean, and the rest is absorbed by the atmosphere. The absorbed solar
energy heats our planet.
As the rocks,
the air, and the seas warm, they radiate “heat” energy (thermal infrared
radiation). From the surface, this energy travels into the atmosphere where
much of it is absorbed by water vapor and long-lived greenhouse gases such as
carbon dioxide and methane.
When they absorb
the energy radiating from Earth’s surface, microscopic water or greenhouse gas
molecules turn into tiny heaters— like the bricks in a fireplace, they radiate
heat even after the fire goes out. They radiate in all directions. The energy
that radiates back toward Earth heats both the lower atmosphere and the
surface, enhancing the heating they get from direct sunlight.
and radiation of heat by the atmosphere—the natural greenhouse effect—is
beneficial for life on Earth. If there were no greenhouse effect, the Earth’s
average surface temperature would be a very chilly -18°C (0°F) instead of the
comfortable 15°C (59°F) that it is today.
The enhanced Greenhouse Effect
What has scientists concerned now is that over the past
250 years, humans have been artificially raising the concentration of
greenhouse gases in the atmosphere at an ever-increasing rate, mostly by
burning fossil fuels, but also from cutting down carbon-absorbing forests.
Since the Industrial Revolution began in about 1750, carbon dioxide levels have increased nearly
38 percent as of 2009 and methane levels have increased 148 percent. Its impact
on weather too can’t be subsided. Recent changes in the weather is directly
related to the process of global warming. In most of the places around the
world, global warming result in more frequent hot days and fewer
cool days, with the greatest warming occurring over land. Longer, more intense
heat waves will become more common. Storms, floods, and droughts will generally
be more severe as precipitation patterns change. Hurricanes may increase in
intensity due to warmer ocean surface temperatures.
It is impossible to pin any single unusual
weather event on global warming, but emerging evidence suggests that global
warming is already influencing the weather. Heat waves, droughts, and intense rain events have increased in frequency during
the last 50 years, and human-induced global warming more likely than not
contributed to the trend.
Rising Sea Levels
The weather isn’t the only thing global warming will
impact: rising sea levels will erode coasts and cause more frequent coastal
flooding. Some island nations will disappear. The problem is serious because up
to 10 percent of the world’s population lives in vulnerable areas less than 10
meters (about 30 feet) above sea level.
Between 1870 and
2000, the sea level increased by 1.7 millimeters per year on average, for a
total sea level rise of 221 millimeters (0.7 feet or 8.7 inches). And the rate of sea level rise is
accelerating. Since 1993, NASA satellites have shown that
sea levels are rising more quickly, about 3 millimeters per year, for a total
sea level rise of 48 millimeters (0.16 feet or 1.89 inches) between 1993 and
Sea levels crept up about 20 centimeters (7.9 inches)
during the twentieth century. Sea levels are predicted to go up between 18 and
59 cm (7.1 and 23 inches) over the next century, though the increase could be
greater if ice sheets in Greenland and Antarctica melt more quickly than
predicted. Higher sea levels will erode coastlines and cause more frequent
The Intergovernmental Panel on Climate Change (IPCC)
estimates that sea levels will rise between 0.18 and 0.59 meters (0.59 to 1.9
feet) by 2099 as warming sea water expands, and mountain and polar glaciers
melt. These sea level change predictions may be underestimates, however,
because they do not account for any increases in the rate at which the world’s
major ice sheets are melting. As temperatures rise, ice will melt more quickly.
Satellite measurements reveal that the Greenland and West Antarctic ice sheets
are shedding about 125 billion tons of ice per year—enough to raise sea levels
by 0.35 millimeters (0.01 inches) per year. If the melting accelerates, the
increase in sea level could be significantly higher.
More importantly, perhaps, global warming is already
putting pressure on ecosystems, the plants and animals that co-exist in a
particular climate zone, both on land and in the ocean. Warmer temperatures
have already shifted the growing season in many parts of the globe. The growing
season in parts of the Northern Hemisphere became two weeks longer in the
second half of the 20th century. Spring is coming earlier in both hemispheres.
This change in
the growing season affects the broader ecosystem. Migrating animals have to
start seeking food sources earlier. The shift in seasons may already be causing
the lifecycles of pollinators, like bees, to be out of synch with flowering
plants and trees. This mismatch can limit the ability of both pollinators and
plants to survive and reproduce, which would reduce food availability
throughout the food chain. Warmer temperatures also extend the growing season.
This means that plants need more water to keep growing throughout the season or
they will dry out, increasing the risk of failed crops and wildfires. Once the
growing season ends shorter, milder winters fail to kill dormant insects,
increasing the risk of large, damaging infestations in subsequent seasons.
ecosystems, maximum daily temperatures might climb beyond the tolerance of
indigenous plant or animal. To survive the extreme temperatures, both marine
and land-based plants and animals have started to migrate towards the poles.
Those species, and in some cases, entire ecosystems, that cannot quickly
migrate or adapt, face extinction. The IPCC estimates that 20-30 percent of
plant and animal species will be at risk of extinction if temperatures climb
more than 1.5° to 2.5°C.
The changes to weather and ecosystems will also affect
people more directly. Hardest hit will be those living in low-lying coastal
areas, and residents of poorer countries who do not have the resources to adapt
to changes in temperature extremes and water resources. As tropical temperature
zones expand, the reach of some infectious diseases, such as malaria, will
change. More intense rains and hurricanes and rising sea levels will lead to
more severe flooding and potential loss of property and life.
and more frequent fires will lead to more cases of heat stroke and deaths, and
to higher levels of near-surface ozone and smoke, which would cause more ‘code
red’ air quality days. Intense droughts can lead to an increase in
malnutrition. On a longer time scale, fresh water will become scarcer,
especially during the summer, as mountain glaciers disappear, particularly in
Asia and parts of North America.
On the flip
side, there could be “winners” in a few places. For example, as long as the
rise in global average temperature stays below 3 degrees Celsius, some models
predict that global food production could increase because of the longer
growing season at mid- to high-latitudes, provided adequate water resources are
available. The same small change in temperature, however, would reduce food
production at lower latitudes, where many countries already face food
shortages. On balance, most research suggests that the negative impacts of a
changing climate far outweigh the positive impacts. Current
civilization—agriculture and population distribution—has developed based on the
current climate. The more the climate changes, and the more rapidly it changes,
the greater the cost of adaptation.
Ultimately, global warming will impact life
on Earth in many ways, but the extent of the change is largely up to us.
Scientists have shown that human emissions of greenhouse gases are pushing
global temperatures up, and many aspects of climate are responding to the
warming in the way that scientists predicted they would. This offers hope.
Since people are causing global warming, people can mitigate global warming, if
they act in time. Greenhouse gases are long-lived, so the planet will continue
to warm and changes will continue to happen far into the future, but the degree
to which global warming changes life on Earth depends on our decisions.
(Author Teaches Sociology at GDC Handwara Kashmir.
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