Climate Change
Climate
Change is the defining issue of our time and we are at a defining moment. From
shifting weather patterns that threaten food production, to rising sea levels
that increase the risk of catastrophic flooding, the impacts of climate change
are global in scope and unprecedented in scale. Without drastic action today,
adapting to these impacts in the future will be more difficult and costly.
The
Evidences of Climatic Change:
1.
Global Temperature Rise
The
planet's average surface temperature has risen about 1.62 degrees Fahrenheit
(0.9 degrees Celsius) since the late 19th century, a change driven largely by
increased carbon dioxide and other human-made emissions into the atmosphere.4
Most of the warming occurred in the past 35 years, with the six warmest years
on record taking place since 2014. Not only was 2016 the warmest year on
record, but eight of the 12 months that make up the year — from January through
September, with the exception of June — were the warmest on record for those
respective months.
2.
Warming Oceans
The
oceans have absorbed much of this increased heat, with the top 700 meters
(about 2,300 feet) of ocean showing warming of more than 0.4 degrees Fahrenheit
since 1969.
3.
Shrinking Ice Sheets
The
Greenland and Antarctic ice sheets have decreased in mass. Data from NASA's
Gravity Recovery and Climate Experiment show Greenland lost an average of 286
billion tons of ice per year between 1993 and 2016, while Antarctica lost about
127 billion tons of ice per year during the same time period. The rate of
Antarctica ice mass loss has tripled in the last decade.
4.
Glacial Retreat
Glaciers
are retreating almost everywhere around the world — including in the Alps,
Himalayas, Andes, Rockies, Alaska and Africa.
5.
Decreased Snow Cover
Satellite
observations reveal that the amount of spring snow cover in the Northern
Hemisphere has decreased over the past five decades and that the snow is
melting earlier
6.
Sea Level Rise
Global
sea level rose about 8 inches in the last century. The rate in the last two
decades, however, is nearly double that of the last century and is accelerating
slightly every year.
7.
Declining Arctic Sea Ice
Both
the extent and thickness of Arctic sea ice has declined rapidly over the last
several decades.
8.
Extreme Events
Glaciers
are retreating almost everywhere around the world — including in the Alps,
Himalayas, Andes, Rockies, Alaska and Africa. The number of record high
temperature events in the United States has been increasing, while the number
of record low temperature events has been decreasing, since 1950. The U.S. has
also witnessed increasing numbers of intense rainfall events.
9.
Ocean Acidification
Since
the beginning of the Industrial Revolution, the acidity of surface ocean waters
has increased by about 30 percent. This increase is the result of humans
emitting more carbon dioxide into the atmosphere and hence more being absorbed
into the oceans. The amount of carbon dioxide absorbed by the upper layer of
the oceans is increasing by about 2 billion tons per year.
Causes
Certain
gases in the atmosphere block heat from escaping. Long-lived gases that remain
semi-permanently in the atmosphere and do not respond physically or chemically
to changes in temperature are described as "forcing" climate change.
Gases, such as water vapor, which respond physically or chemically to changes
in temperature are seen as "feedback."
Gases
that contribute to the greenhouse effect include:
Water
Vapour
The
most abundant greenhouse gas, but importantly, it acts as a feedback to the
climate. Water vapor increases as the Earth's atmosphere warms, but so does the
possibility of clouds and precipitation, making these some of the most
important feedback mechanisms to the greenhouse effect.
Carbon
dioxide (CO2)
A
minor but very important component of the atmosphere, carbon dioxide is
released through natural processes such as respiration and volcano eruptions
and through human activities such as deforestation, land use changes, and
burning fossil fuels. Humans have increased atmospheric CO2 concentration by
more than a third since the Industrial Revolution began. This is the most
important long-lived "forcing" of climate change.
Methane
A
hydrocarbon gas produced both through natural sources and human activities,
including the decomposition of wastes in landfills, agriculture, and especially
rice cultivation, as well as ruminant digestion and manure management associated
with domestic livestock. On a molecule-for-molecule basis, methane is a far
more active greenhouse gas than carbon dioxide, but also one which is much less
abundant in the atmosphere.
Nitrous
oxide
A
powerful greenhouse gas produced by soil cultivation practices, especially the
use of commercial and organic fertilizers, fossil fuel combustion, nitric acid
production, and biomass burning.
Chlorofluorocarbons
(CFCs)
Synthetic
compounds entirely of industrial origin used in a number of applications, but
now largely regulated in production and release to the atmosphere by
international agreement for their ability to contribute to destruction of the
ozone layer. They are also greenhouse gases.
On
Earth, human activities are changing the natural greenhouse. Over the last
century the burning of fossil fuels like coal and oil has increased the
concentration of atmospheric carbon dioxide (CO2). This happens because the
coal or oil burning process combines carbon with oxygen in the air to make CO2.
To a lesser extent, the clearing of land for agriculture, industry, and other
human activities has increased concentrations of greenhouse gases.
The
consequences of changing the natural atmospheric greenhouse are difficult to
predict, but certain effects seem likely:
On
average, Earth will become warmer. Some regions may welcome warmer
temperatures, but others may not. Warmer conditions will probably lead to more
evaporation and precipitation overall, but individual regions will vary, some
becoming wetter and others dryer.
A
stronger greenhouse effect will warm the oceans and partially melt glaciers and
other ice, increasing sea level. Ocean water also will expand if it warms,
contributing further to sea level rise.
Meanwhile,
some crops and other plants may respond favorably to increased atmospheric CO2,
growing more vigorously and using water more efficiently. At the same time,
higher temperatures and shifting climate patterns may change the areas where
crops grow best and affect the makeup of natural plant communities.
The
Role of Human Activity
In
its Fifth Assessment Report, the Intergovernmental Panel on Climate Change, a
group of 1,300 independent scientific experts from countries all over the world
under the auspices of the United Nations, concluded there's a more than 95
percent probability that human activities over the past 50 years have warmed
our planet.
The
industrial activities that our modern civilization depends upon have raised
atmospheric carbon dioxide levels from 280 parts per million to 412 parts per
million in the last 150 years. The panel also concluded there's a better than
95 percent probability that human-produced greenhouse gases such as carbon
dioxide, methane and nitrous oxide have caused much of the observed increase in
Earth's temperatures over the past 50 years.
Solar
Irradiance
It's
reasonable to assume that changes in the Sun's energy output would cause the
climate to change, since the Sun is the fundamental source of energy that
drives our climate system. Indeed,
studies show that solar variability has played a role in past climate changes.
For example, a decrease in solar activity coupled with an increase in volcanic
activity is thought to have helped trigger the Little Ice Age between
approximately 1650 and 1850, when Greenland cooled from 1410 to the 1720s and
glaciers advanced in the Alps.
But
several lines of evidence show that current global warming cannot be explained
by changes in energy from the Sun:
Since
1750, the average amount of energy coming from the Sun either remained constant
or increased slightly. If the warming were caused by a more active Sun, then
scientists would expect to see warmer temperatures in all layers of the
atmosphere. Instead, they have observed a cooling in the upper atmosphere, and
a warming at the surface and in the lower parts of the atmosphere. That's
because greenhouse gases are trapping heat in the lower atmosphere.
Climate
models that include solar irradiance changes can’t reproduce the observed
temperature trend over the past century or more without including a rise in
greenhouse gases.
Effects
Global
climate change has already had observable effects on the environment. Glaciers
have shrunk, ice on rivers and lakes is breaking up earlier, plant and animal
ranges have shifted and trees are flowering sooner.
Effects
that scientists had predicted in the past would result from global climate
change are now occurring: loss of sea ice, accelerated sea level rise and
longer, more intense heat waves.
Scientists
have high confidence that global temperatures will continue to rise for decades
to come, largely due to greenhouse gases produced by human activities. The
Intergovernmental Panel on Climate Change (IPCC), which includes more than
1,300 scientists from the United States and other countries, forecasts a
temperature rise of 2.5 to 10 degrees Fahrenheit over the next century.
According
to the IPCC, the extent of climate change effects on individual regions will
vary over time and with the ability of different societal and environmental
systems to mitigate or adapt to change.
The
IPCC predicts that increases in global mean temperature of less than 1.8 to 5.4
degrees Fahrenheit (1 to 3 degrees Celsius) above 1990 levels will produce
beneficial impacts in some regions and harmful ones in others. Net annual costs
will increase over time as global temperatures increase.
"Taken
as a whole," the IPCC states, "the range of published evidence
indicates that the net damage costs of climate change are likely to be
significant and to increase over time."
Future
Effects
The
amount of heat-trapping gases emitted globally, and how sensitive the Earth’s
climate is to those emissions.
Temperatures
Will Continue to Rise
Because
human-induced warming is superimposed on a naturally varying climate, the
temperature rise has not been, and will not be, uniform or smooth across the
country or over time.
Frost-free
Season (and Growing Season) will Lengthen
The
length of the frost-free season (and the corresponding growing season) has been
increasing nationally since the 1980s, with the largest increases occurring in
the western United States, affecting ecosystems and agriculture. Across the
United States, the growing season is projected to continue to lengthen.
In
a future in which heat-trapping gas emissions continue to grow, increases of a
month or more in the lengths of the frost-free and growing seasons are
projected across most of the U.S. by the end of the century, with slightly
smaller increases in the northern Great Plains. The largest increases in the
frost-free season (more than eight weeks) are projected for the western U.S.,
particularly in high elevation and coastal areas. The increases will be
considerably smaller if heat-trapping gas emissions are reduced.
Changes
in Precipitation Patterns
Average
U.S. precipitation has increased since 1900, but some areas have had increases
greater than the national average, and some areas have had decreases. More
winter and spring precipitation is projected for the northern United States,
and less for the Southwest, over this century.
Projections
of future climate over the U.S. suggest that the recent trend towards increased
heavy precipitation events will continue. This trend is projected to occur even
in regions where total precipitation is expected to decrease, such as the
Southwest.
More
Droughts and Heat Waves
Droughts
in the Southwest and heat waves (periods of abnormally hot weather lasting days
to weeks) everywhere are projected to become more intense, and cold waves less
intense everywhere.
Summer
temperatures are projected to continue rising, and a reduction of soil
moisture, which exacerbates heat waves, is projected for much of the western
and central U.S. in summer. By the end of this century, what have been
once-in-20-year extreme heat days (one-day events) are projected to occur every
two or three years over most of the nation.
Hurricanes
Will Become Stronger and More Intense
The
intensity, frequency and duration of North Atlantic hurricanes, as well as the
frequency of the strongest (Category 4 and 5) hurricanes, have all increased
since the early 1980s. The relative contributions of human and natural causes
to these increases are still uncertain. Hurricane-associated storm intensity
and rainfall rates are projected to increase as the climate continues to warm.
Sea
Level Will Rise 1-8 feet by 2100
Global
sea level has risen by about 8 inches since reliable record keeping began in
1880. It is projected to rise another 1 to 8 feet by 2100. This is the result
of added water from melting land ice and the expansion of seawater as it warms.
In
the next several decades, storm surges and high tides could combine with sea
level rise and land subsidence to further increase flooding in many regions.
Sea level rise will continue past 2100 because the oceans take a very long time
to respond to warmer conditions at the Earth’s surface. Ocean waters will
therefore continue to warm and sea level will continue to rise for many
centuries at rates equal to or higher than those of the current century.
Arctic
Likely to Become Ice-Free
The
Arctic Ocean is expected to become essentially ice free in summer before
mid-century.
The
Human Fingerprint on Greenhouse Gases
- The concentration of GHGs in the earth’s atmosphere is directly linked to the average global temperature on Earth;
- The concentration has been rising steadily, and mean global temperatures along with it, since the time of the Industrial Revolution;
- The most abundant GHG, accounting for about two-thirds of GHGs, carbon dioxide (CO2), is largely the product of burning fossil fuels.
The
UN Intergovernmental Panel on Climate Change (IPCC)
The
Intergovernmental Panel on Climate Change (IPCC) was set up by the World
Meteorological Organization (WMO) and United Nations Environment to provide an
objective source of scientific information. In 2013 the IPCC provided more
clarity about the role of human activities in climate change when it released
its Fifth Assessment Report. It is categorical in its conclusion: climate
change is real and human activities are the main cause.
Fifth
Assessment Report
The
report provides a comprehensive assessment of sea level rise, and its causes,
over the past few decades. It also estimates cumulative CO2 emissions since
pre-industrial times and provides a CO2 budget for future emissions to limit
warming to less than 2°C. About half of this maximum amount was already emitted
by 2011.
The
report found that: From 1880 to 2012, the average global temperature increased
by 0.85°C. Oceans have warmed, the amounts of snow and ice have diminished and
the sea level has risen. From 1901 to 2010, the global average sea level rose
by 19 cm as oceans expanded due to warming and ice melted. The sea ice extent
in the Arctic has shrunk in every successive decade since 1979, with 1.07 × 106
km² of ice loss per decade.
Given
current concentrations and ongoing emissions of greenhouse gases, it is likely
that by the end of this century global mean temperature will continue to rise
above the pre-industrial level. The world’s oceans will warm and ice melt will
continue. Average sea level rise is predicted to be 24–30 cm by 2065 and 40–63
cm by 2100 relative to the reference period of 1986–2005. Most aspects of
climate change will persist for many centuries, even if emissions are stopped.
There
is alarming evidence that important tipping points, leading to irreversible
changes in major ecosystems and the planetary climate system, may already have
been reached or passed. Ecosystems as diverse as the Amazon rainforest and the
Arctic tundra, may be approaching thresholds of dramatic change through warming
and drying. Mountain glaciers are in alarming retreat and the downstream
effects of reduced water supply in the driest months will have repercussions
that transcend generations.
Global
Warming of 1.5°C
In
October 2018 the IPCC issued a special report on the impacts of global warming
of 1.5°C, finding that limiting global warming to 1.5°C would require rapid,
far-reaching and unprecedented changes in all aspects of society. With clear
benefits to people and natural ecosystems, the report found that limiting
global warming to 1.5°C compared to 2°C could go hand in hand with ensuring a
more sustainable and equitable society. While previous estimates focused on
estimating the damage if average temperatures were to rise by 2°C, this report
shows that many of the adverse impacts of climate change will come at the 1.5°C
mark.
The
report also highlights a number of climate change impacts that could be avoided
by limiting global warming to 1.5ºC compared to 2ºC, or more. For instance, by
2100, global sea level rise would be 10 cm lower with global warming of 1.5°C
compared with 2°C. The likelihood of an Arctic Ocean free of sea ice in summer
would be once per century with global warming of 1.5°C, compared with at least
once per decade with 2°C. Coral reefs would decline by 70-90 percent with
global warming of 1.5°C, whereas virtually all (> 99 percent) would be lost
with 2ºC.
The
report finds that limiting global warming to 1.5°C would require “rapid and
far-reaching” transitions in land, energy, industry, buildings, transport, and
cities. Global net human-caused emissions of carbon dioxide (CO2) would need to
fall by about 45 percent from 2010 levels by 2030, reaching ‘net zero’ around
2050. This means that any remaining emissions would need to be balanced by
removing CO2 from the air.
United
Nations legal instruments
United
Nations Framework Convention on Climate Change
The
UN family is at the forefront of the effort to save our planet. In 1992, its
“Earth Summit” produced the United Nations Framework Convention on Climate
Change (UNFCCC) as a first step in addressing the climate change problem.
Today, it has near-universal membership. The 197 countries that have ratified
the Convention are Parties to the Convention. The ultimate aim of the
Convention is to prevent “dangerous” human interference with the climate
system.
Kyoto
Protocol
By
1995, countries launched negotiations to strengthen the global response to
climate change, and, two years later, adopted the Kyoto Protocol. The Kyoto
Protocol legally binds developed country Parties to emission reduction targets.
The Protocol’s first commitment period started in 2008 and ended in 2012. The
second commitment period began on 1 January 2013 and will end in 2020. There
are now 197 Parties to the Convention and 192 Parties to the Kyoto Protocol.
Paris
Agreement
At
the 21st Conference of the Parties in Paris in 2015, Parties to the UNFCCC
reached a landmark agreement to combat climate change and to accelerate and
intensify the actions and investments needed for a sustainable low carbon
future. The Paris Agreement builds upon the Convention and – for the first time
– brings all nations into a common cause to undertake ambitious efforts to
combat climate change and adapt to its effects, with enhanced support to assist
developing countries to do so. As such, it charts a new course in the global
climate effort.
The
Paris Agreement’s central aim is to strengthen the global response to the
threat of climate change by keeping the global temperature rise this century
well below 2 degrees Celsius above pre-industrial levels and to pursue efforts
to limit the temperature increase even further to 1.5 degrees Celsius.
On
Earth Day, 22 April 2016, 175 world leaders signed the Paris Agreement at
United Nations Headquarters in New York. This was by far the largest number of
countries ever to sign an international agreement on a single day. There are
now 186 countries that have ratified the Paris Agreement.
2019
Climate Action Summit
On
23 September 2019, Secretary-General António Guterres convened a Climate Summit
to bring world leaders of governments, the private sector and civil society
together to support the multilateral process and to increase and accelerate
climate action and ambition. He named Luis Alfonso de Alba, a former Mexican
diplomat, as his Special Envoy to lead preparations. The Summit focused on key
sectors where action can make the most difference—heavy industry, nature-based
solutions, cities, energy, resilience, and climate finance. World leaders
reported on what they are doing, and what more they intend to do when they
convene in 2020 for the UN climate conference, where commitments will be
renewed and may be increased. In closing the Climate Action Summit, the Secretary-General
said “You have delivered a boost in momentum, cooperation and ambition. But we
have a long way to go.”
“We
need more concrete plans, more ambition from more countries and more
businesses. We need all financial institutions, public and private, to choose,
once and for all, the green economy.”
Scientific
Consesus
1.
American Association for the Advancement of Science
"Based
on well-established evidence, about 97% of climate scientists have concluded
that human-caused climate change is happening." (2014)
2.
Intergovernmental Panel on Climate Change
“Warming
of the climate system is unequivocal, and since the 1950s, many of the observed
changes are unprecedented over decades to millennia. The atmosphere and ocean
have warmed, the amounts of snow and ice have diminished, and sea level has
risen."
“Human
influence on the climate system is clear, and recent anthropogenic emissions of
greenhouse gases are the highest in history. Recent climate changes have had
widespread impacts on human and natural systems.”
3.
International Academies: Joint Statement
"Climate
change is real. There will always be uncertainty in understanding a system as
complex as the world’s climate. However there is now strong evidence that
significant global warming is occurring. The evidence comes from direct
measurements of rising surface air temperatures and subsurface ocean
temperatures and from phenomena such as increases in average global sea levels,
retreating glaciers, and changes to many physical and biological systems. It is
likely that most of the warming in recent decades can be attributed to human
activities (IPCC 2001)." (2005, 11 international science academies).
Climate Change in NEWS
Response
Option
The
impacts of global climate change in the United States are already being felt
and are projected to intensify in the future, especially without further action
to reduce climate-related risks. As the impacts of climate change grow,
Americans face decisions about how to respond.
Actions
to prepare for and adjust to changing climate conditions—thereby reducing
negative impacts or taking advantage of new opportunities—are known as
adaptation. The other major category of response options—known as
mitigation—involves efforts to reduce the amount and speed of future climate
change by limiting emissions or removing carbon dioxide from the atmosphere.
Adaptation and mitigation actions are linked in multiple ways and can be
considered complementary strategies—mitigation efforts can reduce future risks,
while adaptation can minimize the consequences of changes that are already
happening as a result of past and present emissions.
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