Scientists are worried about the amount of carbon dioxide in the atmosphere and how fast it continues to build without showing any sign of slowing, writes James Warner
SOMETHING happened on Earth on Thursday last that scientists believe the planet hasn’t experienced in as many as 5m years.
Atop the Mauna Loa Observatory on the Big Island of Hawaii, sensors tracking all the substances swirling around in Earth’s atmospheric soup are — for the first time — recording carbon dioxide at levels higher than at any time in human history.
Carbon dioxide, shorthanded as CO2, is the primary greenhouse gas emitted into the air when people burn fossil fuels. It traps heat in the atmosphere that would normally radiate back into space. Simply put, the more carbon dioxide, the hotter we get.
Scientists express the level of carbon dioxide according to how many molecules of CO2 are floating around in a million molecules of air — the “parts per million” measurement, or “ppm”. On Thursday, CO2 in the atmosphere surpassed a new milestone of 400.03 ppm, according to the National Oceanic and Atmospheric Administration (NOAA). The Scripps Institution of Oceanography, which also tracks the number, recorded a slightly lower number of 399.73.
The fact that CO2 levels have hit 400 ppm comes as no surprise to scientists who have watched the number steadily climb since around 1780, the start of the Industrial Revolution. Then, CO2 levels were about 280 ppm. By 1958, when scientist Charles Keeling began measuring CO2 on Mauna Loa (known today as the Keeling Curve), the number had risen to 317 ppm.
Scientists have long predicted that an unprecedented period of human prosperity built on the use of oil and coal would come with dark side effects for the climate.
“This generation has altered the composition of the atmosphere on a global scale,” US president Lyndon Johnson told Congress in 1965, through “a steady increase in carbon dioxide from the burning of fossil fuels”.
What worries scientists in 2013 is not only the amount of CO2 in the atmosphere, but how fast it continues to build up without showing any sign of slowing or even stabilising.
Today’s rate of carbon dioxide increase is more than 100 times faster than the increase that occurred when the last ice age ended, NOAA said.
Unless emissions are slowed, scientists tell us babies being born today will enter their 30s as the CO2 level reaches 450 ppm.
Without a concerted worldwide effort to curb greenhouse gas emissions, scientists predict global warming will produce a cockeyed climate concoction laced with increasing numbers of heatwaves, melting glaciers, higher sea levels and more extreme weather.
‘We are seeing climate change on steroids’
A GROUP of climate scientists, experts, and historians have given their thoughts on the 400 ppm milestone.
Richard CJ Somerville, distinguished professor emeritus and research professor, Scripps Institution of Oceanography, University of California, San Diego:
Today we are watching human-caused climate change occur. It is not a problem for the future. It is happening here and now. Melting Arctic sea ice and rising sea level are examples. Extreme weather events today occur in a changed environment. The heat-trapping gases and particles that humanity emits into the atmosphere increase the odds of severe weather events, just as steroids taken by a baseball player can increase the odds of home runs. Today we are seeing climate change on steroids. To limit global warming to moderate or tolerable amounts, the entire world must act quickly to reduce these emissions. That we have failed to do this is a tragedy.
George Luber, associate director for climate and health, Centers for Disease Control and Prevention:
Climate change is already impacting health in the US. Wildfires and extreme weather events are becoming more frequent, air pollutants and allergens are becoming more concentrated, and the habitats for disease-carrying rodents and insects are shifting. We can manage the unavoidable, by adapting to the effects that are already occurring, but we also need to avoid the unmanageable, by preventing the most severe impacts. As climate-related threats increase, our opportunities to adapt may be limited. Acting now to prevent the worst impacts of climate change will have most health benefits.
Richard Norris, professor of paleobiology and curator of geological collections, Scripps Institution of Oceanography:
The last time Earth saw 400 ppm CO2 in the atmosphere about 3m-4m years back. There were camels and forests in the Arctic, the tropics were locked in a near constant El Niño.
Archaeologists note that people started to grow crops as soon as the climate was constant enough to have some assurance we could make a harvest the next year. But beyond 400 ppm is a shift into heat waves, deep droughts, and torrential rains, and a less predictable world of snowpocalypse, Hurricane Sandy, and Texas-sized fires. The worst of it is that we are already committed to several thousand years of unsettled climate thanks to approximately 150 years of carbon pollution.
But, if we do nothing, CO2 emissions will hit approximately 1,000 ppm by the end of the century — a scenario that results in more than 10,000 years of radically changing climate. Tell your kids not to go into farming, disaster insurance, or beachfront real estate.
Andrew Gettelman, climate scientist, National Center for Atmospheric Research:
The carbon dioxide concentration in air tells two stories. It varies like a clock, rhythmically marking the annual cycle of the biosphere (plants) breathing in CO2 in the spring, and exhaling in the autumn. There is also a general upward tick from year to year. The trend is from society exhaling CO2 as the waste product of energy and agriculture: It feeds us, heats us, and moves us. We borrow CO2 from the past (fossil fuels), and give it to the future (in the atmosphere).
The laws of physics say that has consequences. Warmer temperatures on average. Shifts in rain patterns. Extreme wet and dry conditions we have not seen in recorded climate. We can choose how much CO2 we emit. As we slowly push it up, we could slowly push it down.
Someday, our choices will be recorded in the CO2 record itself. Where will the trend go? How hard will the planet be breathing? That is the story we continue to write into the record.
Jeffrey Kiehl, senior scientist, US National Center for Atmospheric Research:
Continuing on our current energy path will lead to projected carbon dioxide levels of around 1,000 ppm by 2100, a mere 90 years in the future. At that point, we will have returned Earth’s carbon dioxide levels to that of the extremely warm Eocene, a time more than 30m years ago in which there were no large ice sheets.
We now realise the increase in carbon dioxide is not a theoretical problem, but one of immense importance for the wellbeing of all life on Earth. Do we now have the wisdom to avoid a return to Earth’s deep warm past?
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