Friday, July 3, 2015

Oceans face massive and irreversible impacts without carbon cuts – study

The risks currently being experienced across the planet.
Most, if not all, are set to increase.
Regional changes in the physical system and associated risks for natural and human-managed systems.
Source: Science; Gattuso et al. (2015) modified from IPCC WGII AR5 (2014).

Business-as-usual carbon emissions would cause global warming that brings serious ocean acidification, death of corals and mangroves, scientists say

Time is rapidly running out for the world’s oceans and the creatures that live in them as the Earth’s climate continues to warm, say scientists.
Only “immediate and substantial” reductions in greenhouse gas emissions can hope to prevent “massive” impacts on marine ecosystems, warn the experts.
Researchers compared the fate of the oceans under two scenarios, one a “business-as-usual” approach and the other involving drastic cuts in emissions.
Their analysis showed that business-as-usual would have an enormous and “effectively irreversible” impact on ocean ecosystems and the services they provide, such as fisheries, by 2100.
Even after curbing emissions of carbon dioxide (CO2) enough to prevent temperatures rising by more than 2C compared with pre-industrial levels, many marine ecosystems would still suffer significantly, they said.

The international team led by Dr Jean-Pierre Gattuso, from the Laboratoire d’OcĂ©anographie de Villefranche in France, wrote in the journal Science: “Impacts on key marine and coastal organisms, ecosystems, and services from anthropogenic (man-made) CO2 emissions are already detectable, and several will face high risk of impacts well before 2100, even with the stringent CO2 emissions scenario.
“These impacts are occurring across all latitudes and have become a global concern that spans the traditional north/south divide.”
Any new global climate agreement that fails to minimise the impact on oceans will be “incomplete and inadequate”, stressed the scientists.

 Changes in ocean physics and chemistry and impacts on organisms and ecosystem services according to stringent (RCP2.6) and high business-as-usual (RCP8.5) CO2 emissions scenarios.

The findings are intended to inform the forthcoming 2015 United Nations climate change conference in Paris.
By 2050, the loss of critical habitats such as coral reefs and mangroves was expected to contribute to “substantial declines” for tropical fisheries, on which many human communities depended, said the researchers.
This was the case even under the 2C emission cutting scenario.
While Arctic fisheries may benefit from warmer temperatures at first, the scientists pointed out that this region was a “hot spot” of ocean acidification.
It also contained communities that were highly reliant on the sea.

Acidification, warmer oceans, sea level rise threaten the all marine that video, the Ocean Initiative 2015 Project provides straightforward answers to this issue.

A new paper just published in Science summarizes the projected impacts of climate change on the world’s oceans, and consequently on humans and our economy.
The study concludes that global warming beyond the international limit of 2°C above pre-industrial temperatures would pose serious threats to marine ecosystems and their millions of human dependents.
It builds on the consensus science published by the Intergovernmental Panel on Climate Change last year.
The study concludes,
Ocean changes associated with a 2°C warming of global surface temperature carries high risks of impacts and should not be exceeded.

The oceans have absorbed over 90% of the excess heat and 28% of the carbon pollution generated by human consumption of fossil fuels. 
As the authors of the paper note, in many regions, the ocean plays an important role in the livelihood and food supply of human populations.
The ocean represents more than 90% of the Earth’s habitable space, hosts 25% of eukaryotic species, provides 11% of global animal protein consumed by humans, protects coastlines, and more.

‘Irreversible change’ to sea life from CO2
A major report warns that life in the seas will be irreversibly changed unless CO2 emissions from industrial society are drastically cut.
Twenty-two experts in the journal Science say the oceans are heating, losing oxygen and becoming more acidic - all in response to our carbon dioxide.
The scientists in Germany have been studying an event five million years ago that could throw light on today's challenges.

The study considers human impacts on the world’s oceans under two different scenarios.
The first is a business-as-usual high fossil fuel consumption scenario (called RCP8.5 in the latest IPCC report), and the second is a scenario in which humans take immediate serious steps to curb fossil fuel consumption (called RCP2.6).
Between now and 2100, RCP8.5 involves 6 times more global carbon pollution emitted by humans than RCP2.6.

The societal effort involved in reducing fossil fuel consumption and carbon emissions to meet RCP2.6 is obviously much greater than the effort involved in the do-nothing scenario, but this study finds that the outcomes are also starkly different for the world’s oceans.
In the business-as-usual scenario, by 2100 the oceans would be about 30 cm higher, oxygen content nearly 2% lower, ocean acidity 70% higher, and sea surface temperatures about 2°C hotter than in RCP2.6.
The authors write,
In summary, the carbon that we emit today will change the Earth System irreversibly for many generations to come. The ocean’s content of carbon, acidity, and heat as well as sea level will continue to increase long after atmospheric CO2 is stabilized. These irreversible changes increase with increasing emissions, underscoring the urgency of near-term carbon emission reduction if ocean warming and acidification are to be kept at moderate levels.

"Oceans - The sinks of our World": gives an example of how public engagement can make a significant contribution to scientific investigations of the effects of global warming and ocean acidification on marine life.
The film introduces us to a man who has been recording the temperature of the sea in his region of the Mediterranean Sea for forty years.
Now he is also collecting water samples to support scientific investigations on ocean acidification.
His work is of great importance to scientists who are studying the impacts of increasing emission of CO2, driven by human fossil fuel combustion, on the temperature and chemical make- up of our oceans.
Questions about the impact ocean acidification may have already caused to the health and diversity of marine life need to be answered.
However, questions about how the conditions for marine organisms may change in the future also matter greatly.
After all, experimental research in the laboratory and observations of marine life close to undersea volcanic vents have already shown that that calcifying organisms, such as chorals, are greatly affected by an increase of acidity in the water.
The film invites the viewer to observe scientific investigations in the laboratory but more so to join scientists as they conduct their investigations at under water sites.

As an example of one consequence of these changes, many marine species are shifting to different geographic regions as the oceans warm.
These shifts can pose serious challenges for fisheries.
Recent studies strongly reiterate that many species—including various invertebrates, commercially important fish species and marine mammals—are undergoing phenological and geographical shifts of up to 400 km per decade as a result of warming.

These geographical species shifts are projected to occur about 65% faster in the business-as-usual scenario than under RCP2.6.
Coral reefs are particularly sensitive to human-caused ocean changes.
They provide habitat for almost a quarter of the species in the oceans.
Hundreds of millions of people rely on the coastal protection, tourism, and food provided by coral reef ecosystems.
However, the authors of this study note that the dual threats of global warming and ocean acidification pose a serious threat to coral reefs.
Reef-building corals are extremely vulnerable to warming.
Warming causes mass mortality of warm-water corals through bleaching as well as through biotic diseases, resulting in declines in coral abundance and biodiversity.
Coral reefs can recover from bleaching events when thermal stress is minimal and of short duration.
However, ocean warming and acidification are expected to act synergistically to push corals and coral reefs into conditions that are unfavorable for coral reef ecosystems.
There is limited agreement and low confidence on the potential for corals to adapt to rapid warming.

The study also estimates some of the economic impacts of ocean changes in the business-as-usual scenario.
For example, lost coastal habitats and sea level rise could combine to expose 0.2 to 4.6% of the global population to inundation annually at a cost of 0.3 to 9.3% to global GDP.
In terms of tourism dollars, the difference between the two scenarios amounts to about $10 billion per year, hitting Australia and the USA particularly hard.
Loss of coral reefs to tourism under the RCP2.6 and RCP8.5 scenarios could cost between US$1.9 billion and US$12 billion per year, respectively. 
Coral reef losses due to ocean warming and acidification on the Great Barrier Reef place up to $5.7 billion and 69,000 jobs in Australia at risk.
In addition, ocean acidification may cause an annual loss of reef ecosystem services that are valued up to US$1 trillion by 2100.
For about a quarter of countries with reef-related tourism, mainly less developed countries, this kind of tourism accounts for more than 15% of gross domestic product and is more sustainable than extractive livelihoods.

The study also makes a critical and often-overlooked point.
Some people believe geoengineering is a better or more practical solution than curbing our carbon pollution.
Geoengineering proposals often involve slowing global warming by reducing the amount of sunlight absorbed by the Earth, for example by pumping sulfur high into the atmosphere, or putting large mirrors into orbit.
However, these proposals wouldn’t curb human carbon emissions, and hence wouldn’t slow the accumulation of carbon in the oceans, or the resulting ocean acidification.
Ultimately, the authors warn that immediate action to cut carbon pollution is critical if we want to curb the rapid and dangerous impacts already being observed in the world’s oceans.
…immediate and substantial reduction of CO2 emissions is required in order to prevent the massive and effectively irreversible impacts on ocean ecosystems and their services that are projected with emissions scenarios more severe than RCP2.6. Limiting emissions to below this level is necessary to meet UNFCCC’s stated objectives. Policy options that overlook CO2, such as solar radiation management and control of methane emission, will only minimize impacts of ocean warming and not those of ocean acidification.

Links :
  • BBC : CO2 emissions threaten ocean crisis

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