Uitstoot van CO2 moet binnen 40 jaar naar nul anders…*
Uit verschillende studies concluderen wetenschappers van het Carnegie instituut en de Oregon State universiteit dat voor 2050 de uitstoot van CO2 tot nul zal moeten worden gereduceerd wil de aarde niet voor de meeste mensen onbewoonbaar worden, en dat gebeurt als de temperatuur 2°C of meer gaat stijgen. Vorig jaar werd ongeveer 10 miljard ton CO2 uitgestoten en momenteel stijgt deze hoeveelheid nog steeds waardoor de hoeveelheid CO2 in de atmosfeer inmiddels op 380 ppm gekomen is. Het gevolg van de CO2 uitstoot is dat laatste 150 jaar de temperatuur op aarde al 0,8 °C gestegen is. Volgens de laatste computermodellen zal de uitstoot van CO2 de komende 40 jaar moeten reduceren tot nul om binnen die 2°C temperatuurstijging te blijven. Maar dan nog zullen de CO2 waarden in de lucht hoger zijn dan 450 ppm, een waarde waarbij het ecologische leven in de oceanen volgens een andere studie grotendeels wordt verwoest door onder meer de verzuring als gevolg van de CO2. De politieke en
economische wil zal er moeten zijn om de CO2 uitstoot op tijd tot nul te reduceren zo stellen de onderzoekers, want technisch kan het wel.
Carbon Emissions Must be Cut to Near Zero to Avert Climate Disaster, Warn Researchers
A series of recently published studies have determined that humanity must cease all emission of carbon dioxide by 2050 to avoid catastrophic climate change.
Currently, humans are responsible for roughly 10 billion tons of carbon emissions each year, a rate that continues to
rise.
"The question is, what if we don't want the Earth to warm anymore?" said Ken Caldeira of the Carnegie Institute. "The answer implies a much more radical change to our energy system than people are thinking
about."
The Earth's average temperature has already increased by 1.4 degrees Fahrenheit since the Industrial Revolution. Should that temperature increase reach 3.6 degrees, scientists warn, the effects would lead to global catastrophe, decimating water and food sources worldwide.
To date, efforts to prevent further global warming have mostly focused on limiting the total amount of greenhouse gases, such as carbon dioxide, in the atmosphere. The new studies instead focus on keeping the planet's temperature below the 3.6-degree threshold.
According to Oregon State University researcher Andreas Schmittner, author of another study, current greenhouse gas emission rates would lead to a 7.2 degree temperature increase by 2100. A gradual reduction of emissions to zero by 2300 would lead to a 15 degree temperature rise.
Using computer models, Caldeira and Schmittner's research teams modeled different carbon-reduction scenarios, taking into account effects like deep-sea warming, which is triggered by greenhouse gas emissions and continues to raise the temperature of the planet on its
own.
"I was struck by the fact that the warming continues much longer even after emissions have declined," Schmittner said. "Our actions right now will have consequences for many, many generations. Not just for a hundred years, but thousands of years."
"Each unit of carbon dioxide emissions must be viewed as leading to quantifiable and essentially permanent climate change on centennial timescales," Caldeira and colleagues
wrote.
The question of whether to cut emissions to zero is not one of technology, Caldeira said, but of political and economic
will.
"In the end, this is a value judgment," he said.
Coral Reefs Need Deep CO2 Cutbacks Soon
Wednesday, September 24, 2008
Stanford, CA—How much carbon dioxide is too much? According to the United Nations Framework Convention on Climate Change, greenhouse gases in the atmosphere need to be stabilized at levels low enough to “prevent dangerous anthropogenic interference with the climate system.” But scientists have come to realize that an even more acute danger than climate change is lurking in the world’s oceans—one that is likely to be triggered by CO2 levels that are modest by climate standards.
Ocean acidification could devastate coral reefs and other marine ecosystems even if atmospheric carbon dioxide stabilizes at 450 ppm, a level well below that of many climate change forecasts, report chemical oceanographers Long Cao and Ken Caldeira of the Carnegie Institution’s Department of Global Ecology in the journal Geophysical Research Letters.
The researchers’ conclusions are based on computer simulations of ocean chemistry stabilized at atmospheric CO2 levels ranging from 280 parts per million (pre-industrial levels) to 2000 ppm. Present levels are 380 ppm and rapidly rising due to accelerating emissions from human activities, primarily the burning of fossil fuels.
This study was initiated as a result of Caldeira’s testimony before a Congressional subcommittee on Fisheries, Wildlife and Oceans in April of 2007. At that time he was asked what stabilization level would be needed to preserve the marine environment, but had to answer that no such study had yet addressed that question. Cao and Caldeira’s study helps fill the gap.
Atmospheric CO2 absorbed by the oceans’ surface water produces carbonic acid, the same acid that gives soft drinks their fizz, making certain carbonate minerals dissolve more readily in seawater. This is especially true for aragonite, the mineral used by corals and many other marine organisms to grow their skeletons. For corals to be able to build reefs, which requires rapid growth and strong skeletons, the surrounding water needs to be highly supersaturated with
aragonite.
“Before the industrial revolution, over 98% of warm water coral reefs were surrounded by open ocean waters at least 3.5 times supersaturated with aragonite” says Cao. “But even if atmospheric CO2 stabilizes at the current level of 380 ppm, fewer than half of existing coral reef will remain in such an environment. If the levels stabilize at 450 ppm, fewer than 10% of reefs would be in waters with the kind of chemistry that has sustained coral reefs in the past.”
For the ecologically productive cold waters near the poles, the prospects are equally grim, says Cao. “At atmospheric CO2 levels as low as 450 ppm, large parts of the Southern Ocean, the Arctic Ocean, and the North Pacific would experience a rise in acidity that would violate US Environmental Protection Agency water quality standards.” Under those conditions the shells of many marine organisms would dissolve, including those at the base of the food
chain.
“If current trends in CO2 emissions continue unabated,” says Caldeira, “in the next few decades, we will produce chemical conditions in the oceans that have not been seen for tens of millions of years. We are doing something very profound to our oceans. Ecosystems like coral reefs that have been around for many millions of years just won’t be able to cope with the
change.”
“When you go to the seashore, the oceans seem huge,” he adds. “It’s hard to imagine we could wreck it all. But if we want our children to enjoy a healthy ocean, we need to start cutting carbon emissions now.”
(September
2008)
