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?

HealthWeather-related mortalityInfectious diseasesAir-quality respiratory illnesses

AgricultureCrop yieldsIrrigation demandsPest outbrreaks

Water ResourcesChanges in water supplyWater qualityIncreased competition for water

Coastal AreasErosion of beachesInundation of coastal landsCosts to protect coastal communities

ForestsChange in forest compositionShift geographic range of forestsForest health and productivityPest outbreaks

Species and Natural AreasShift in ecological zonesLoss of habitat and species

Potential Climate Change ImpactsPotential Climate Change Impacts

Climate Changes

Sea Level Rise

Temperature

Precipitation

Source: EPA

Recent Global Temperature Trends

Are We Experiencing Global Warming Now?

2005 is now #1

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?

What Controls Global Warming?

Where Do You Go To Find Records of Climate Change?

Antarctica

Vostok

ice core

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 strengthGreen hatched area: range of signal strengths in PCM model

with anthropogenic forcing included (Barnett et al, 2005)

Models of Future Warming

Will temperature increase be

uniform across the

globe?

+10°F

Differential Temp Change

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

2050 2100Annual Temperature Change from 1975-95 to 2040-60 (°C)

-3 - -2

0 - 1

3 - 4

6 - 7

8 - 9

12 - 15

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 CenturyGeneral 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

Retreat of 7 miles and 800 meter thinning. Source: National Snow and Ice Data Center

1941 2004

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 Greenland2001

Helheim Glacier on Greenland2005

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.

From Stocker, T. F., 1996.

Future CO2 vs NADW Formation

What Has Sea Level Been Doing?

Sea Level Rise – “Non-Catastrophic”

People at Risk from Sea-level RisePeople 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.

Source: R. Nicholls, Middlesex University in the U.K. Meteorological Office. 1997. Climate Change and Its Impacts: A Global Perspective.

People at Risk from a 17-inch Sea-level People at Risk from a 17-inch Sea-level Rise by the 2080s*Rise by the 2080s*

*Assuming 1990s level of flood protection*Assuming 1990s level of flood protection

Source: EPA

Louisiana Shoreline Change Louisiana Shoreline Change with a 20-inch Rise in Sea Levelwith a 20-inch Rise in Sea Level

Lake CharlesLafayette

Baton Rouge

Morgan City

Houma

NewOrleans

Gulf of Mexico

Land Lost

South FloridaSouth FloridaShoreline Shoreline Change with a Change with a 1m Rise1m Risein Sea Levelin Sea Level

Source: EPA

U.S. East Coast Flooding U.S. East Coast Flooding with a 1m Rise in Sea Levelwith a 1m Rise in Sea Level

Source: EPA

Bangladesh Flooding Bangladesh Flooding with a 1.5m Rise in Sea Levelwith a 1.5m Rise in Sea Level

Flooding in the Sacramento-San Joaquin Delta

Increased Frequency of Floods

• 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 – “Catastrophic”

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.

Sea Level Rise – Up 6m

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