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CO2

Carbon Dioxide Levels Reach Unprecedented Highs: But Catastrophic Climate Change Can Still be Avoided

Alan Miller's picture

 Courtesy of World Meteorological Organization
Graph shows concentrations of atmospheric Co2 for the last 800,000 years, with measurements, starting from 1958, made at Mauna Loa in Hawaii. - Image courtesy of World Meteorological Organization

Scientists monitoring atmospheric concentrations of CO2 from a mountaintop in Hawaii recently reported that the presence of this greenhouse gas exceeded 400 parts per million (ppm) for the first time in at least three million years – a period when temperatures were much warmer than today. The significance of this seemingly dry statistical trend is stunning as reported in the New York Times:

From studying air bubbles trapped in Antarctic ice, scientists know that going back 800,000 years, the carbon dioxide level oscillated in a tight band, from about 180 parts per million in the depths of ice ages to about 280 during the warm periods between. The evidence shows that global temperatures and CO2 levels are tightly linked.

In addition to the location in Hawaii, several other Global Atmosphere Watch stations from the Arctic to the Equator reported CO2 concentrations exceeding 400ppm.

Experts believe that in order to limit warming to 2°C – a goal based on expected impacts – concentrations should rise to no more than 450 ppm, a level we may reach in only about 25 years based on current trends.

Giving oceans a fighting chance

Mary Barton-Dock's picture

Last week I went swimming with manta rays, sharks and dolphins along some of the world’s most spectacular reefs. Well at least, it felt like I was swimming among them. With my special 3D glasses on, it was as if I was flying across coral atolls, plunging through clouds of jellyfish and darting in and out of brightly colored corals alongside hundreds of thousands of tropical fish.

In a new film by Luke Cresswell and Steve McNicholas – The Last Reef 3D: Cities Beneath the Sea – viewers embark on a worldwide journey to explore coral reef habitats from Palau and French Polynesia in the Pacific to the Bahamas in the Caribbean.

As visually stunning as the film is, it carries a very sobering message: human activity is having a significant negative impact on the world’s oceans.

Many of us who work on climate change and oceans have known about the threat from ocean acidification and warming for a long time. Increasing carbon dioxide emissions have resulted in rising surface and air temperatures. Moreover, ocean acidity is rising owing to an increased absorption of carbon dioxide from the atmosphere. Increasing acidity levels in turn make it harder for corals to grow and for shell-forming animals like mussels to build their protective housing, leading to knock-on effects of biodiversity loss in ocean called “dead zones”.

The movie’s message is reinforced by a recent report published in Science Magazine which says the oceans are acidifying at a pace not seen in 300 million years. Historically, ocean acidification has led to mass extinctions. What makes today’s situation particularly alarming is that the rise in CO2 is not due to volcanic eruptions or other natural occurrences but is the direct consequence of human behavior over the course of the last century or so.

The buzz around blue carbon

Marea E. Hatziolos's picture

Photo credit: J. TamelanderThe delegates and observers at the COP16 in Cancun are getting an earful about Blue Carbon—shorthand for atmospheric carbon sequestered in the earth’s coastal and nearshore environments. Oceans Day at Cancun will feature a session on Blue Carbon, and briefs, and blogs by ocean advocates are circulating on the net and at side events. The reason for the buzz is that coastal wetlands, including tidal salt marshes, estuaries and river deltas, mangroves and sea grass beds are highly efficient at taking up CO2 from the atmosphere and converting it into organic material—then storing it in the soil. In fact, the root systems and sediment layers which build up as this organic material is generated, broken down and deposited, are up to ten times more rich in carbon than the biomass above the surface.

 

This makes coastal wetlands even better at sequestering carbon than tropical forests. And, unlike their counterparts on land whose net growth peaks when the forest matures, wetland vegetation continues to grow and sequester carbon in the soil as long as sediments are deposited and the environment remains healthy. This is why Blue Carbon is being brought into the international dialogue on carbon emission offsets and the domain of REDD+ eligible activities. A statement, signed by 55 marine and environmental stakeholders from 19 countries has been presented to the COP for action.

Should South Africa tax carbon emissions?

Shanta Devarajan's picture

Since it is the poorest continent, produces less than 4 percent of global greenhouse gas emissions, and was not responsible for the build-up of CO2 in the atmosphere, there is a strong case that Africa should not have to constrain its growth by mitigating greenhouse gas emissions in the future.  The one exception may be South Africa, which produces 65 percent of Africa’s (and 1.5 percent of the world’s) emissions and, as a middle-income country, may have the capacity to curb emissions in the future.  In a recent paper, Delfin Go, Sherman Robinson, Karen Thierfelder and I explore the costs to the South African economy of a tax on carbon emissions.