09.09.2014 - Natural Sciences Sector

Record Greenhouse Gas Levels Impact Atmosphere and Oceans

Time series of de-seasonalized surface seawater pH and respective trendlines (left) and of de-seasonalized surface pCO2 (μatm) and respective trendlines (right).

The amount of greenhouse gases in the atmosphere reached a new record high in 2013, propelled by a surge in levels of carbon dioxide, according to the World Meteorological Organization’s annual Greenhouse Gas Bulletin. For the first time, this Bulletin contains a section on ocean acidification prepared in collaboration with the International Ocean Carbon Coordination Project (IOCCP) of the Intergovernmental Oceanographic Commission of UNESCO (IOC-UNESCO), the Scientific Committee on Oceanic Research (SCOR), and the Ocean Acidification International Coordination Centre (OA-ICC) of the International Atomic Energy Agency (IAEA).

The conclusions of the Greenhouse Gas Bulletin inject even greater urgency into the need for concerted international action against accelerating and potentially devastating climate change. It shows that between 1990 and 2013 there was a 34% increase in radiative forcing – the warming effect on our climate – because of long-lived greenhouse gases such as carbon dioxide (CO2), methane and nitrous oxide.

The ocean currently absorbs one-fourth of anthropogenic CO2 emissions, reducing the increase in atmospheric CO2 that would otherwise occur because of fossil fuel combustion. Enhanced ocean CO2 uptake alters the marine carbonate system and lead to increasing acidity. The ocean's acidity increase is already measurable as the ocean takes up about 4 kilogrammes of CO2 per day per person.

The current rate of ocean acidification appears unprecedented at least over the last 300 million years, based on proxy-data from paleo archives. In the future, acidification will continue to accelerate at least until mid-century, based on projections from Earth system models.

The potential consequences of ocean acidification on marine organisms are complex. A major concern is the response of calcifying organisms, such as corals, algae, mollusks and some plankton, because their ability to build shell or skeletal material (via calcification) depends on the abundance of CO2. For many organisms, calcification declines with increased acidification. Other impacts of acidification include reduced survival, development, and growth rtes as well as changes in physiological functions and reduced biodiversity.

"The inclusion of a section on ocean acidification in this issue of WMO’s Greenhouse Gas Bulletin is appropriate and needed. It is high time the ocean, as the primary driver of the planet’s climate and attenuator of climate change, becomes a central part of climate change discussions,” said Wendy Watson-Wright, Executive Secretary of IOC-UNESCO.

If global warming is not a strong enough reason to cut CO2 emissions, ocean acidification should be, since its effects are already being felt and will increase for many decades to come.  I echo WMO Secretary General Jarraud’s concern – we ARE running out of time,” she said.

In 2013, concentration of CO2 in the atmosphere was 142% of the pre-industrial era (1750). The observations from WMO’s Global Atmosphere Watch (GAW) network showed that CO2 levels increased more between 2012 and 2013 than during any other year since 1984. Preliminary data indicated that this was possibly related to reduced CO2 uptake by the earth’s biosphere in addition to the steadily increasing CO2 emissions.

Carbon dioxide remains in the atmosphere for many hundreds of years and in the ocean for even longer. Past, present and future CO2 emissions will have a cumulative impact on both global warming and ocean acidification. The laws of physics are non-negotiable,” said Mr Jarraud.

There is only one way to reduce the trend: cutting emissions drastically. The Greenhouse Gas Bulletin provides a scientific base for decision-making. Knowledge and tools are available to act and try to contain global warming.

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