Dangerous Climate Change
Addendum to
McGuire, B (2007). Dangerous Climate Change: Rising
Sea-levels and Ocean Circulation Changes. Issues in
Risk Science, vol. 5. Benfield Hazard Research Centre.
Dangerous Climate Change
Specific indicators of dangerous climate change
include:
• circumstances that could lead to global and
unprecedented consequences,
• extinction of iconic species (e.g., the Polar
Bear),
• loss of entire ecosystems or human cultures,
• a threat to water resources, and
• a significant rise in mortality rates.
Dangerous Climate Change
Examples include:
• the collapse and melting of the Greenland
or West Antarctic ice sheets, leading to
wholesale, catastrophic sea-level rise.
• a shutdown or significant slow-down in the
Atlantic Thermohaline Circulation
(including the Gulf Stream), spawning
bitterly cold winters in the UK and Europe.
Can we think of other possible examples?
Potential Climate Change Impacts
Health
Weather-related mortality
Infectious diseases
Air-quality respiratory illnesses
Agriculture
Crop yields
Climate Changes Irrigation demands
Pest outbrreaks
Forests
Temperature Change in forest composition
Shift geographic range of forests
Forest health and productivity
Pest outbreaks
Precipitation
Water Resources
Changes in water supply
Water quality
Sea Level Rise Increased competition for water
Coastal Areas
Erosion of beaches
Inundation of coastal lands
Costs to protect coastal communities
Species and Natural Areas
Shift in ecological zones
Loss of habitat and species
Source: EPA
Are We Experiencing Global Warming Now?
2005 is now #1
Recent Global Temperature Trends
What Controls Global Warming?
Hansen et al., 2005. Science vol. 308
What Controls Global Warming?
Hansen et al., 2005. Science vol. 308
What
Controls
Global
Warming?
What Controls Global Warming?
Where Do You Go To Find Records of
Climate Change?
Antarctica
ice core
Vostok
The Change in Temperature
Depends on Where You Are
Last 50 Years Surface Temperature Change Based on Linear Trends
Observed and modeled ocean temp. changes
Hansen et al., 2005. Science vol. 308
Observed and modeled ocean temp. changes
Red circles: observed warming signal strength
Green hatched area: range of signal strengths in PCM model
with anthropogenic forcing included (Barnett et al, 2005)
+10°F
Models of
Future
Warming
Will
temperature
increase be
uniform
across the
globe?
Differential Temp Change
2050 Annual Temperature Change
2100
from 1975-95 to 2040-60 (°C)
-3 - -2 6-7
0-1 8-9
3-4 12 - 15
The results are based on climate change simulations made with the Coupled
Global Climate Model developed by Environment Canada. From Atlas of
Canada http://atlas.gc.ca/site/english/maps/climatechange/scenarios/globalannualtemp2100
Why Different Temps at Same Latitude?
The Thermohaline Circulation a.k.a.
the “Global Conveyor Belt”
Thermohaline Circulation in
Cross-Section
CO2
Thermohaline Circulation in
Cross-Section
Models of Future Global Warming
General Predictions of Impacts over 21st Century
Source - IPCC WGII TAR 2001 Thanks to Martha Groom
Hurricane Power Dissipation Index (PDI)
PDI has increased
dramatically in recent
decades in both the
Atlantic and Pacific Ocean
basins. From Emanuel
(2005)
Alpine Glacier Retreat
1941 2004
Retreat of 7 miles and 800 meter thinning. Source: National Snow
and Ice Data Center
Sea Ice Loss Over Time
Source: National Snow and Ice Data Center
Northern
Hemisphere Sea
Ice Extent
(1979 versus 2003)
Image courtesy of NASA-Goddard Space
Flight Center
Northern Hemisphere Sea Ice Thickness
Greenland Ice Sheet Meltdown
Helheim Glacier on Greenland
2001
Helheim Glacier on Greenland
2005
Glacier flow has doubled since 2001. Benfield Hazard Research Centre (2006)
Northeast Atlantic Salinity
Modeled Impact of Thermohaline
Current Shutdown
• Temperatures across Europe and eastern
North America would fall by ~ 4° C within
20 years, bringing chillier summers and
appalling winters.
• Weakening of the Indian Monsoon and
halving of rainfall in parts of Central and
South America. This could slash
agricultural productivity and place what
remains of the Amazon Rainforest in peril.
Modeled Impact of Thermohaline
Current Shutdown
Winter temps in Europe would frequently plunge below -10°C
Change in annual temperature 30 years after a
collapse of the thermohaline circulation
From Michael Vellinga, Hadley Centre and the Climatic Research Unit
Potential Impacts of Thermohaline
Shutdown
From Schwartz, P and Randall, D, 2003.
Future CO2 vs NADW Formation
From Stocker, T. F., 1996.
What Has Sea Level Been Doing?
Sea Level Rise – “Non-Catastrophic”
People at Risk from Sea-level Rise
• In 1990, it was estimated that around 1.2 billion
people (~ 23 percent of the global population)
lived within the coastal zone This includes more
than 250 million inhabitants of 14 of the world’s
megacities (population = 10 million).
• By 2015, more than 340 million people will live in
21 megacities, 18 of which will occupy coastal
locations. The highest population densities are
encountered below the 20 m elevation.
• The near-coastal population could rise as high
as 5.2 billion by the 2080s.
People at Risk from a 17-inch Sea-level
Rise by the 2080s*
*Assuming 1990s level of flood protection
Source: R. Nicholls, Middlesex University in the U.K. Meteorological Office. 1997. Climate Change and Its Impacts:
A Global Perspective.
Louisiana Shoreline Change
with a 20-inch Rise in Sea Level
Baton Rouge
Lafayette
Lake Charles New
Orleans
Morgan City
Houma
Gulf of Mexico
Land Lost
Source: EPA
South Florida
Shoreline
Change with a
1m Rise
in Sea Level
U.S. East Coast Flooding
with a 1m Rise in Sea Level
Source: EPA
Bangladesh Flooding
with a 1.5m Rise in Sea Level
Source: EPA
Flooding in the Sacramento-
San Joaquin Delta
Increased Frequency of Floods
Sea Level Rise – “Catastrophic”
• The rate of melting of the Greenland Ice Sheet
has doubled in the last 10 years, from 96 km3 in
1996 to 220 km3 in 2005, with three of the
biggest glaciers draining the ice sheet doubling
their rates of sliding seawards in the last 7 years.
• A local temperature rise of just 2.7° C
(corresponding to a global rise of less than 2° C)
is predicted to result in irreversible melting of the
Greenland Ice Sheet and an eventual ~ 7 m
sea-level rise.
• This threshold could be reached as early as
2050.
Sea Level Rise – “Catastrophic”
• Increased ice loss is also occurring in Antarctica,
where the West Antarctic Ice Sheet is now losing
about 150 km3 a year.
• Over the last 50 years, an area of ice shelves
the size of Jamaica have broken up and melted,
while on the Antarctic Peninsula, the Pine Island
and Thwaites glaciers are now moving three
times faster than 10 years ago.
• Melting of these glaciers alone would raise sea-
levels by more than a metre, with complete
melting of the West Antarctic Ice Sheet raising
global sea-levels by ~ 5 m.
Sea Level Rise – Up 6m
The question is not… “Will it happen?”
It’s “How soon?”
Initial estimates had the Greenland Ice
Sheet melting completely in 1,000 years.
Now looking more like a few centuries.
Greenland Ice Sheet Meltdown
Antarctica – The Wild Card
West Antarctic Ice Sheet
West
Antarctic
Ice Sheet Ross Ice
Shelf
Models of Future Global Warming
2050
Sea Level Rise Associated with collapse of West Antarctic Ice Sheet
Models of Future Global Warming
2050
Sea Level Rise Associated with collapse of West Antarctic Ice Sheet
Models of Future Global Warming
2050
Sea Level Rise Associated with collapse of West Antarctic Ice Sheet