Candidates for Global Change "Surprise"

(entries not intended to be comprehensive or independent)

A. Anthropogenic Forcing Functions

• South remains proportionately behind the North in economic development.
• Transfer of wealth from South to North accelerates, widening the economic disparities between the two.
• The nation state demises, leading to conflict and collapse of economic growth.
• An underclass of nations is maintained owing to the diminished process of globalization.
• World mortality patterns are transformed by the emergence of a new, highly contagious virus.
• Medical technology increases life expectancy substantially.
• Human population growth rate does not decrease; the demographic transition does not happen globally.
• The smooth population trajectory foreseen in all standard projections of world population becomes woefully inaccurate in the face of sharp departures from them.
• Funding stops for technology development that would facilitate a low carbon future.
• Change takes place in the political consciousness of the value of nature and the will to act accordingly.
• The global market does not dominate (control) natural resource allocation locally, especially for land and water use; rather non- market institutions (e.g., control economies, quasi-market economies, local institutions) remain important.
• India matches China in CO₂ emissions.
• Siberia incurs large-scale resource depletion/degradation and deforestation.
• Several catastrophic nuclear plant accidents lead to ban on nuclear power before inexpensive non-carbon backstop technology is available.
• A very inexpensive, noncarbon backstop technology is developed.
• China burns its coal without significant improvement in technology efficiency.
• China shifts to low-carbon alternative energy source (e.g., finds ample supply of natural gas or develops viable biomass industry).
• Energy use reverts to a parallel track with economic growth because (i) the cost of energy conservation proves too expensive and/or (ii) a switch from an industrial to a service economy proceeds slowly.
• CO2 emissions from developing countries do not increase.
• Land-cover change stabilizes in South America and South East Asia; deforestation slows dramatically.
• Synergism of habitat fragmentation, chemical assault, introduction of exotic species, and anthropogenic climate change affect biodiversity in unforeseen ways.
• Spatially varying (regional scale) competing forces create unforeseen regional climate anomalies (e.g., land-use changes, aerosols, or tropospheric ozone).
• Chemical pollution causes significant genetic change in humans and other species, possibly affecting fertility.

B. Nonanthropogenic Forcing Functions

• A gradual reduction in "conveyor belt" oceanic overturning leading to cooling at high latitudes occurs, despite general (but slower) global warming.
• Heat stored in the ocean at intermediate depths is released to the atmosphere, leading to rapid warming.
• Stratospheric cooling causes increased Polar Stratospheric Clouds and loss of ozone.
• Antarctic volcanoes lubricate ice-stream flow causing glacial surge and rapid sea level rise.
• The Greenland ice sheet surges.
• Changes in volcanism are induced by changes in climate.
• High latitude forests are not a CO₂ sink.
• Dimethyl sulfide emissions decline with reduced sea ice.
• Dimethyl sulfide emissions change with sea-surface temperature change.
• Positive or negative biogeochemical feedbacks become climate forcing.

C. Environmental Consequence

• Regional climate anomalies lead to economic and political dislocations.
• Regional environmental degradation has global impacts on economic and political systems.
• Differential movement of species ranges in response to global environmental change causes irreversible or very long-term ecological damage (extinctions or cascading effects).
• Warmer climate could be more stable/less variable.
• Enhanced hydrological cycle leads to unanticipated extreme floods or droughts.
• Cloud liquid water increases causing increased cloud albedo and negative feedbacks on warming.
• Increased snow accumulation compensates faster outflow in West Antarctica when the Ross Ice Shelf disintegrates.
• Land-cover stabilizes in South America.
• Hurricane intensity changes with warming.

D. Human Response to the Advent or Prospect of Global Change

• Geoengineering is adopted.
• The climate convention increases funding for low-cost noncarbon backstop technologies.
• The creation of wildlife reserves and migration corridors lowers impact on biodiversity.
• Improved climate-change scenarios and better understanding of climate impacts identifies specific winners and losers and thereby destroys consensus in the international community for emissions reductions.
• CO₂ build-up stalls for five years, derailing the current convention process.
• Society chooses to be relatively carbon free and resilient to climate change.