The Earth is now in uncharted territory as atmospheric carbon dioxide has shot past the 400 ppm mark. There is no more room for manoeuvre

When Brian Lara scored a scintillating 400 not out in Antigua in April 2004, it seemed his score would remain unchallenged for the foreseeable future. But we now have another player on the scene who has scored 400, and threatens to go past that number effortlessly — carbon dioxide (CO2); CO2 levels in the atmosphere touched 400 parts per million (ppm) on May 9. Its symbolic significance is huge, its actual import is even bigger, for three reasons.

Impact on life cycles

One, the recent pace at which CO2 levels have been rising to reach 400 ppm. When Charles Keeling [the world’s leading authority on atmospheric greenhouse gas accumulation and climate science pioneer] began measuring atmospheric CO2 in March 1958, and through the 1960s, CO2 emissions were found to be rising at a little over half a ppm a year. The world economy was at a much lower level than today notwithstanding post-War growth, and carbon emissions were commensurately lower. By the late 1990s this had changed, spurred primarily, but not exclusively, by the shifting of manufacturing to China, and capitalism’s desire to cut costs of energy inputs and labour. CO2 rise in the first decade of this century made the collective jaw of climate scientists drop. Despite the world economic crisis since 2007, annual carbon dioxide emissions from burning fossil fuels have been rising in recent years, to 32 billion tonnes (plus another four billion tonnes from deforestation and even more of other gases). Eight billion tonnes of CO2 in the atmosphere equals 1 ppm. So even though the Earth absorbs — is being forced to absorb — twice as much CO (roughly 17-18 billion tonnes a year currently) as it used to 50 years ago, atmospheric CO2 levels have been galloping three times as fast, at a little over two ppm a year for the last decade.

This is 20,000 times the long-term natural rate at which carbon dioxide has gone into and out of the atmosphere as part of the carbon cycle. A consequence, usually rendered invisible as we tend to be so anthropocentric, is the oceans getting more acidic, with harmful effects on corals and some marine species.

This pace of emissions and consequent warming is also making it increasingly difficult for ecosystems and species to adapt. A metasurvey by Prof. Camille Parmesan [University of Texas, Austin] of 866 published studies reported species across the world struggling to cope with disruptions in the life cycles of predators and prey, of insect pollinators and flowering plants. Birds are laying their first eggs earlier. As their habitat gets warmer, other species are trying to move away from the Equator or climb higher. Consequently, mountaintop and polar species have suffered contractions in their range or “been the first groups in which whole species have gone extinct due to recent climate change.”

Two, as we reach 400 ppm and beyond, we are going farther away from safe levels of CO2. Albeit a minority view, but a growing one, safe has been deemed as 350 ppm or lower. In its first articulation in 2008, [leading climate scientist] James Hansen and others wrote that “if humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, … CO2will need to be reduced … to at most 350 ppm, but likely less than that” (“Target Atmospheric CO2: Where Should Humanity Aim?,” The Open Atmospheric Science Journal, 2008, 2, pp. 217-31). This paper provides the intellectual basis for the worldwide campaign to reduce CO2, headed by the organisation, 350.org.

Temperature regulator

Three, the influence of CO2 levels on the Earth’s temperatures and hence climate over the past 50 million years should give us pause. In The Long Thaw (Princeton 2009), Professor David Archer, who works on the global carbon cycle at the University of Chicago, writes: “The similarity between CO and temperature in [the] Antarctica is jaw-dropping,” a causal link he says that’s even stronger than that between smoking and lung cancer, “kind of a gold standard in the medical world.” Falling CO2 levels contributed to the formation of ice caps on the Antarctic 34 million years ago. As CO2 levels fell further, to roughly 240 ppm three million years ago, temperatures fell in their wake sufficiently for ice to form in the Arctic. That’s why Arctic ice is now the first to go. I have not come across any work on the potential impact of ice-free Arctic summers on India’s climate, but you can bet your last rupee they will be considerable. CO2 was also one of two big factors in the Earth moving in and out of Ice Age glacials over the past 2.5 million years. It is this regulator of the Earth’s temperature that we have been shortsightedly fiddling with, and pushed beyond the realms of human experience.

We don’t want to go much beyond 400 ppm. CO2 has one quality of the other great batsman of the last 25 years — longevity. A significant portion of CO2 emitted remains in the atmosphere for several millennia. Climate change is also largely irreversible for a thousand years after emissions stop.

(Nagraj Adve is an activist based in Delhi and works on issues connected with global warming. E-mail: nagraj.adve@gmail.com)

This article has been corrected for a techincal coding error wherein earlier CO2 (cardon dioxide) appeared as CO (carbon monoxide) .

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