Impacts of climate change due to the human-caused trend of global warming are now becoming evident, and these impacts are only a faint rumbling of future climate impacts if substantial mitigating action is not taken soon. While impacts due to natural climate change have always occurred, global warming accentuates these impacts. For the earth as a whole, these extra impacts will be overwhelmingly negative. Regionally and temporally, there will be variations.
The basic reason is simple - more energy due to the global warming trend of climate change on the whole produces more impact.
While nothing will ever be 100% certain, and while attribution for many impacts can only be deduced statistically, expert opinion warns us that a variety of disasters awaits if we continue with "Business as Usual". To get an idea, think of smoking. While individual cases cannot be "proved", it is statistically irrefutable that smoking leads to a variety of horrible diseases and deaths. Prudent risk management says "don't smoke", and prudent risk management says "mitigate global warming".
Related articles on global warming impacts with references and links are on this Climate Portal. See the IPCC Impacts report below for detailed documentation.
Water Shortages: Glaciers and snow packs that now provide water to many millions of people are melting, foreshadowing severe regional water shortages in the future. HERE are the slides of a review by Dr Peter Gleick "The Vulnerability of U.S. Water Resources to Climate Change: From the Mississippi River floods to growing shortages in the West" presented to the US House of Representatives in partnership with the American Association for the Advancement of Science (AAAS).
Food Disruption: Disruption of food supplies, agriculture, and fisheries will occur drastically for many hundreds of millions, conservatively, by 2100. Increased rain in the winter and increased evaporation in the summer in addition to pest migration will stress crops. This will lead to bad food shortages, including in the US; see HERE and the NASA VIDEO below. Global warming is negatively affecting pollination and bees, said to be responsible for 1/3 of human nutrition. HERE is an article backed by extensive data (explained HERE), showing that fish crucial for the marine food chain are in danger of decreasing by over 50% due to the extension of OMZ (oxygen minimum zones), due to global warming. Global phytoplankton, at the base of the marine food chain, is in decline due to rising sea temperature; see HERE. The earth already has 800 million people that go to bed hungry each night. Global warming will substantially increase this number.
Health Risks: From the American Public Health Association APHA: “Climate change is one of the most serious public health threats facing our nation,” said Georges C. Benjamin, MD, FACP, FACEP (E), executive director of APHA. “Yet few Americans are aware of the very real consequences of climate change on the health of our communities, our families and our children.”
Disease Increase: As warming occurs, disease vectors including insects move north. This will increasingly affect the disease transmission to people, crops, and forests in many regions. The US Defense Department's Quadrennial Review (2010) says: "Climate change will contribute to food and water scarcity, will increase the spread of disease, and may spur or exacerbate mass migration."
Climate-Induced Migration: Food and water shortages, coupled with sea level rise in costal regions, will lead to migration of many millions of displaced and desperate people. HERE is a presentation by Dr. Pamela McElwee (Rutgers U.) entitled "Climate Change and Migration", see HERE for a general discussion.
More Wars and Breakdown of Peace: Tensions between nations stressed by water and food shortages, along with migrations, will lead to more wars. There are some indications that these factors were the underlying cause of the tragic Darfur conflict. Political instability will increase. Terrorism due to desperate groups will likely increase. National security risks related to climate change have been emphasized by many US high level retired military officers and government officials (HERE), and by the US Department of Defense (HERE). The Center for Climate Energy and Security website has a number of links.
Increased probability of Economics and Finance System Breakdown: Crisis events have exhibited the fragility of the worldwide financial and economic systems. The severe environmental and political strains due to global warming impacts, coupled with the mass psychological effects of fear, may well severely further impact financial and economic stability worldwide, including Europe and the United States. The World Economic Forum used its annual Global Risks report to urge policy leaders to step up efforts to tackle the three big dangers cited by a panel of 1,000 experts: severe income disparities, the indebted state of governments and rising greenhouse gas emissions.
Marine Life in Oceans: "Fundamental and comprehensive" changes to marine life include rapidly warming and acidifying oceans, changes in water circulation and expansion of dead zones within the ocean depths.
Droughts: As warming occurs, more evaporation occurs, causing more regional droughts.Picture below: drought damaged corn (US)
Stronger Fires: As warming occurs, more precipitation causes more underbrush to grow, which dries during the summer, providing tinder for wildfires. For example, note the recent increases in California fires and Arizona/New Mexico fires, the worst since the last Ice Age (picture below):
Stronger Hurricanes: Although there are competing factors, there is evidence that global warming may well be increasing the strength of the largest hurricanes, see HERE. See the video below for SANDY.
More Sea Level Rise and Disappearing Ice: Recent evidence shows that glaciers in Antarctica are disintegrating at a faster rate than before, due to complex ice dynamics. If these glaciers disintegrate or slide into the ocean from the land, sea level rise will be measured in meters, and will affect hundreds of millions of people. Coastal regions in many parts of the world will be flooded. Time scales for such effects are being substantially revised from the previous IPCC estimates (which mentioned but did not quantitatively include these effects) to shorter times. See the "Copenhagen Diagnosis" report. According to the National Security Implications of Climate Change for U.S. Naval Forces (2011): RECOMMENDATION 3.1: Based on recent peer-reviewed scientific literature, the Department of the Navy should expect roughly 0.4 to 2 meters global average sea-level rise by 2100, with a most likely value of about 0.8 meter. Projections of local sea-level rise could be much larger and should be taken into account for naval planning purposes.
Fragile Government stress and Failed States: This is increasingly being mentioned as a distinct possibility for some underdeveloped countries stressed by global warming effects without sufficient resources to adapt. The Department of Defense Quadrennial Review 2010 Report says (p85): "Assessments conducted by the intelligence community indicate that climate change could have significant geopolitical impacts around the world, contributing to poverty, environmental degradation, and the further weakening of fragile governments."
More Extinctions: Many species (animals and plants) will become extinct. HERE is a summary and HERE is a great video. An article on University of Exeter research gives the estimate that one in 10 species could face extinction by the year 2100 if current climate change impacts continue.
More Extreme Weather:More energy in the atmosphere due to global warming means more energy is available to produce more extreme weather events than would occur naturally. See HERE and videos below.
HERE is Hurricane Sandy as viewed Oct 29, 2012 from the International Space Station. Global warming "loads the dice" for extreme events by putting more energy into the weather system, as noted by Dr. Jim Hansen in 1988. HERE is Prof. Scott Mandia speaking on Sandy, mentioning models that accurately forecast Sandy's trajectory.
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