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The shoreline of Glacier Bay in Alaska has gone from ice-covered to ice-free due to climate change. A United Nations report finds that warming oceans, retreating glaciers and rising sea levels all produce effects that impact human health on a global scale.

Tim McKenna

Whether from rising sea levels, warming waters or melting glaciers and permafrost, the impact of climate change on the oceans and the coldest regions of the Earth is set to have a profound effect on people no matter where they live, a new UN report suggests.

The report, released Wednesday by the Intergovernmental Panel on Climate Change, also makes clear that the consequences will become more severe the longer it takes policy makers to find solutions for reducing greenhouse gas emissions worldwide.

The findings focus specifically on climate change in the oceans and cryosphere (a collective term for the frozen parts of the planet). Many are relevant to Canada, where northern and coastal communities are already living with the reality of climate change in a world that is 1 degree Celsius warmer, on average, than it was during preindustrial times.

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Scientists behind a landmark study of the links between oceans, glaciers, ice caps and the climate delivered a stark warning to the world on Wednesday: slash emissions or watch cities vanish under rising seas, rivers run dry and marine life collapse. Reuters

For students and activists preparing for school walkouts and climate rallies in multiple cities later this week, the report bolsters the case that there is little time to lose to avert the worst effects of climate change decades from now if the global average temperature rises by two degrees or more.

Among the report’s more startling data points:

  • sea-level rise in a two-degree warmer world could submerge the homelands of 280 million people by the end of the century;
  • “once per century” high-water events for many coastal communities will eventually occur at least annually;
  • the occurrence of marine heatwaves, which reduce the productivity of fisheries, has doubled since 1982 and will increase 20-fold by the end of the century even if global warming is held to two degrees;
  • in 30 years, 70 per cent of infrastructure in communities across the Arctic will be at risk from melting permafrost;
  • if emissions continue unabated, glaciers in mid-latitude countries will lose approximately 80 per cent of their mass by the end of the century, affecting the water supply of hundreds of millions of people.

“We cannot simply say ‘out of sight out of mind,’" said Chris Derksen, a climate scientist with Environment and Climate Change Canada, who was among the report’s lead authors. “The changes that happen in remote places don’t just affect those remote places.”

past and future changes

in the ocean

Historical changes

Projections

Observed

Best-case scenario

Modelled

High emissions scenario

HOT WATER

Projections show a steady rise in average ocean surface temperature if carbon emissions continue unabated. A warmer ocean, particularly in the tropics, means less productive fisheries.

Global mean sea surface temperature

Change relative to 1986-2005, in celsius

5°C

Shaded range indicates 90% likely

4

3

Average

2

1

0

-1

1950

2000

2050

2100

ICE LOSS

Disappearing sea ice is changing Arctic ecosystems and the communities that depend on them. Ice loss also increases warming because less sunlight is reflected into space.

Arctic Sea ice extent (September)

Percentage change relative to 1986-2005

Shaded range indicates 90% likely

50%

0

Average

-50

-100

1950

2000

2050

2100

HIGH SEAS

Average sea level is expected to increase by about half a metre by 2100 but a bigger impact on coastal communities will be the increasing frequency of high water events that formerly occurred only once per century

Once per century

Sea level height and recurrence frequency

Once per decade

Once per century

Once per year

Once per decade

Once per month

Once per year

Average sea level

Once per month

Sea level

rise

Average sea level

Time

Recent past

Future

Diagram is schematic and not to scale

THE GLOBE AND MAIL, SOURCE: iPCC

past and future changes in the ocean

Historical changes

Projections

Observed

Best-case reduced emissions

Modelled

High emissions scenario

HOT WATER

Projections show a steady rise in average ocean surface temperature if carbon emissions continue unabated. A warmer ocean, particularly in the tropics, means less productive fisheries.

Global mean sea surface temperature

Change relative to 1986-2005, in celsius

5°C

Shaded range indicates 90% likely

4

3

Average

2

1

0

-1

1950

2000

2050

2100

ICE LOSS

Disappearing sea ice is changing Arctic ecosystems and the communities that depend on them. Ice loss also increases warming because less sunlight is reflected into space.

Arctic Sea ice extent (September)

Percentage change relative to 1986-2005

50%

Shaded range indicates 90% likely

25

0

Average

-25

-50

-75

-100

1950

2000

2050

2100

HIGH SEAS

Average sea level is expected to increase by about half a metre by 2100 but a bigger impact on coastal communities will be the increasing frequency of high water events that formerly occurred only once per century

Sea level height and recurrence frequency

Once per century

Once per decade

Once per century

Once per year

Once per decade

Once per month

Once per year

Average sea level

Once per month

Sea level

rise

Average sea level

Time

Recent past

Future

Diagram is schematic and not to scale

THE GLOBE AND MAIL, SOURCE: iPCC

past and future changes in the ocean

Historical changes

Projections

Observed

Best-case reduced emissions

Modelled

High emissions scenario

HOT WATER

Projections show a steady rise in average ocean surface temperature if carbon emissions continue unabated. A warmer ocean, particularly in the tropics, means less productive fisheries.

 

Global mean sea surface temperature

Change relative to 1986-2005, in celsius

Shaded range

indicates 90% likely

5°C

4

Average

3

2

1

0

-1

1950

2000

2050

2100

ICE LOSS

Disappearing sea ice is changing Arctic ecosystems and the communities that depend on them. Ice loss also increases warming because less sunlight is reflected into space.

Arctic Sea ice extent (September)

Percentage change relative to 1986-2005

Shaded range

indicates 90% likely

50%

25

Average

0

-25

-50

-75

-100

1950

2000

2050

2100

HIGH SEAS

Average sea level is expected to increase by about half a metre by 2100 but a bigger impact on coastal communities will be the increasing frequency of high water events that formerly occurred only once per century

Once per century

Sea level height and recurrence frequency

Once per decade

Once per century

Once per year

Once per decade

Once per month

Once per year

Average sea level

Once per month

Sea

level

rise

Average sea level

Time

Recent past

Future

Diagram is schematic and not to scale

THE GLOBE AND MAIL, SOURCE: iPCC

More than 100 experts from 36 countries were involved in the report, which drew on the results of about 7,000 scientific publications.

Like others before it – including a companion report issued last month that focused on grasslands, forests and agriculture – the document is intended to be a factual starting point to inform policy makers about the latest scientific thinking on climate change. But increasingly, it ties the physical causes behind the warming of the planet to the expected effects on individuals and communities and to measures that would help lessen those effects if governments act.

“For me the things that really stand out are the impact on food security, food safety and nutrition,” said Sherilee Harper, an environmental epidemiologist at the University of Alberta and lead author on the report’s opening chapter.

Among the side effects of a warming ocean is an increase in marine pathogens that can contaminate seafood and present health hazards, Dr. Harper said. While this can be mitigated to some extent by better monitoring, the risks cannot be entirely eliminated, particularly under a scenario in which countries fail to hold to emissions targets.

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William Cheung, a co-ordinating author and a marine ecologist with the University of British Columbia’s Institute for the Oceans and Fisheries, added that such a scenario could lead to a 20-per-cent reduction in ocean productivity by the end of the century. The problem could be particularly acute in coastal regions in the tropics, as sea life shifts in response to warming surface waters, but it will also have an impact on fishing communities, including Indigenous communities, in the North.

To some extent the impacts of climate change will be unavoidable, including at least half a metre of sea-level rise over the next century. But fish stocks and other marine life that are important for human nutritional needs can be given room to adjust with more responsible and sustainable management.

“If we can reduce impacts, that’s always better. We can help an ecosystem be more resilient over time,” said Susanna Fuller, senior project manager with the advocacy group Oceans North.

A larger concern is that some effects cannot be mitigated if carbon emissions are not capped near current levels and steadily reduced. For example, in a business-as-usual scenario in which emissions continue to rise, the loss of sea ice by the end of the century will transform the Arctic beyond recognition and accelerate warming worldwide because less sunlight will be reflected away from the planet.

“Once the ice goes, the chances of putting the genie back in the bottle are really slight,” said Paul Crowley, who heads up Arctic efforts for WWF Canada. “It’s not just that it’s going to impact you, but once it’s done it will be beyond you being able to do anything about it.”

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