Positive

Negative

Agriculture

• Improved agriculture in some high latitude regions (Mendelsohn 2006)
• Increased growing season in Greenland (Nyegaard 2007)
• Increased productivity of sour orange trees (Kimball 2007)

Agriculture

• Decreasing human water supplies, increased fire frequency, ecosystem change and expanded deserts (Solomon 2009)
• Decline in rice yields due to warmer nighttime minimum temperatures (Peng 2004, Tao 2008)
• Increase of Western United States wildfire activity, associated with higher temperatures and earlier spring snowmelt (Westerling 2006)
• Encroachment of shrubs into grasslands, rendering rangeland unsuitable for domestic livestock grazing (Morgan 2007)
• Decreased water supply in the Colorado River Basin (McCabe 2007)
• Decreasing water supply to the Murray-Darling Basin (Cai 2008)

Health

• Winter deaths will decline as temperatures warm (HPA 2007)

Health

• Increased deaths to heatwaves – 5.74% increase to heatwaves compared to 1.59% to cold snaps (Medina-Ramon 2007)
• Increased heat stress in humans and other mammals (Sherwood 2010)
• Spread in mosquite-borne diseases such as Malaria and Dengue Fever (Epstein 1998)
• Increase in occurrence of allergic symptoms due to rise in allergenic pollen (Rogers 2006)

Arctic Melt

• An ice-free Northwest Passage, providing a shipping shortcut between the Pacific and Atlantic Oceans (Kerr 2002, Stroeve 2008)

Arctic Melt

• Loss of 2/3 of the world’s polar bear population within 50 years (Amstrup 2007)
• Less compacted ice, hazardous floes and more mobile icebergs posing increased risk to shipping (IICWG 2009)
• Drying of arctic ponds with subsequent damage to ecosystem (Smol 2007)

Warming causes methane to escape from Arctic regions, contributing additional greenhouse warming. The following have been observed:

• Melting of Arctic lakes leading methane bubbling (Walter 2007)
• Leakage of methane from the East Siberian Shelf seabed sediments (Shakhova 2008)
• Escape of methane gas from the seabed along the West Spitsbergen continental margin (Westbrook 2009)

Environment

• Greener rainforests due to higher sunlight levels due to fewer rain clouds (Saleska 2009)
• Enhanced plant growth, particularly in Amazon rain forests due mainly to decreased cloud cover and the resulting increase in sunlight (Nemani 2003).
• Increased vegetation activity in high northern latitudes (Zhou 2001)
• Increase in chinstrap and gentoo penguins (Ducklow 2006)
• Increased plankton biomass in the North Pacific Subtropical Gyre (arguably ENSO/PDO might be dominant influence) (Corno 2006)
• Recent increase in forest growth (McMahon 2010)
• Bigger marmots (Ozgul 2010)
• Increased Arctic tundra plant reproduction (Klady 2010)

Environment

• Rainforests releasing CO2 as regions become drier (Saleska 2009)
• Extinction of the European land leech (Kutschera 2007)
• Decrease in Adélie penguin numbers  (Ducklow 2006)
• Disruption to New Zealand aquatic species such as salmonids, stream invertebrates, fishes (Ryan 2007)
• Oxygen poor ocean zones are growing  (Stramma 2008, Shaffer 2009)
• Increased mortality rates of healthy trees in Western U.S. forest (Pennisi 2009)
• More severe and extensive vegetation die-off due to warmer droughts (Breshears 2009)
• Increased pine tree mortality due to outbreaks of pine beetles (Kurz 2008,Bentz 2010)
• Increased risk of coral extinction from bleaching and disease driven by warming waters (Veron 2009, Carpenter 2008)
• Decline in lizard populations (Sinervo 2010)
• Decline in global phytoplankton (Boyce 2010)
• Decline in global net primary production – the amount of carbon absorbed by plants (Zhao 2010)

Ocean Acidification

Note: this is not caused by warming temperatures but by the oceans absorbing more carbon dioxide (Dore 2009).

• Oceans uptake of carbon dioxide, moderates future global warming (Orr 2005)

Ocean Acidification

• Substantial negative impacts to marine ecosystems (Orr 2005, Fabry 2008,Kroeker 2010)
• Inhibiting plankton development, disruption of carbon cycle (Turley 2005)
• Increased mortalities of sea urchins (Miles 2007)
• Threat to fish populations (Munday 2010)

Glacier Melt

Glacier Melt

• Severe consequences for at least 60 million people dependent on ice melt for water supply (Barnett 2005, Immerzeel 2010)
• Contribution to rising sea levels (Pfeffer 2008, Vermeer 2009)

Economical

• Increased cod fishing leading to improved Greenland economy (Nyegaard 2007)

Economical

• Economic damage to poorer, low latitude countries (Mendelsohn 2006)
• Billions of dollars of damage to public infrastructure (Larsen 2007)
• Reduced water supply in New Mexico (Hurd 2008)
• Increased risk of conflict (Zhang 2007) including increased risk of civil war in Africa (Burke 2009)
• Drop in primary productivity due to unprecedented warming at Lake Tanganyika (Tierney 2010)

Sea Level Rise

Sea Level Rise

• Hundreds of millions displaced within this century (Dasgupta 2009)
• Coastal erosion in Nigeria (Okude 2006