In the greenhouse adjacent to my lab, I grow dozens of species of tropical plants. Orchids, bromeliads, banana palms, cycads, and ferns are among my favorites. With its warm, wet air and lush-green visage, the little hothouse is a much loved spot for my students and colleagues during Roanoke’s harsh winter months.
For me, the word, greenhouse, evokes blissful images of color along with rousing fragrances and rich earthy smells. A moment of quiet work in my greenhouse carries me ardently into faraway exotic landscapes like Amazonia and the Yucatán, two of my favorite places in the tropical world.
The word, greenhouse, also calls to mind another, more pernicious relevance: climate change. Climate change in this context refers to any change in climate over time that is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over comparable time periods. A natural greenhouse effect exists to keep Earth warmer than it would be without its atmosphere, thanks to its cozy blanket of carbon dioxide, methane, water vapor, and other so-called greenhouse gases. It turns out that these invisible gases in the planet’s atmosphere act like the glass walls in my greenhouse: the translucent glass allows solar radiation into the structure but traps the resulting heat to keep the interior toasty warm.
We know, however, that changes in the atmospheric abundance of greenhouse gases and aerosols as well as in solar radiation and in land surface properties can alter the energy balance of the climate system. If the balance in the amounts and fluxes of greenhouse gases shifts, then Earth’s overall climate will change accordingly.
For our day, two big questions concern us humans.
Have humans impacted Earth’s atmosphere in any measurable ways? The short answer: yes, definitely. Examples include increases in the amount of atmospheric greenhouse gases from industrial and agricultural activities, particularly carbon dioxide from fossil fuels, and increases in particulates from industrial pollution and deforestation.
Have humans been drivers of climate change? The short answer: yes, extremely likely. Global atmospheric concentrations of carbon dioxide have increased markedly as a result of human activities since the 18th century and now far exceed pre-industrial values as determined from ice cores spanning many thousands of years. Given the strong correlation between carbon dioxide content of the atmosphere and temperature, it follows that increasing concentrations of greenhouse gases lead to increasing temperatures and, consequently, to sudden and dramatic surprises in the world’s climate.
In early December, I was one of more than 27,000 attendees at the COP16 United Nations Climate Change Conference in Cancún, Mexico. The international gathering was upbeat, organized, focused, and hope-filled as world leaders attempted to find sustainable solutions to one of Earth’s greatest environmental challenges. Uninformed and misleading comments by pundits and politicians notwithstanding, the science behind climate change is robust and convincing. Even that silly incident in November 2009, dubbed “Climategate” by the media, involving hacked e-mails of climate scientists from the University of East Anglia did not compromise the science but only a handful of scientists. Does it come as a surprise that scientists are human and, thus, have their faults and foibles like anyone else – including the Glenn Becks and Rosh Limbaughs of the world as they babble on with their off-base fiction? The conference put to rest “Climategate” as a tempest in a teapot and then addressed significant topics related to climate change.
A few of the take-home messages from my participation in the conference: (1) the evidence for global warming is unequivocal based on actual observations with the most rapid warming since the 1950’s and very likely (95% probability) anthropogenic, (2) the array of disinformation must be countered with a succinct, constructive narrative, (3) fear is not a sustainable emotion, but hope is, and (4) science has done its job regarding such a pervasive and complex issue as climate change.
One of the witches in Shakespeare’s Macbeth, prophesied, “Something wicked this way comes.” The wicked thing, of course, is the murderer and traitor, Macbeth, but she could have been talking about climate change with its human causes, all of them ultimately selfish, ominous, and blinkered. Climate change is upon us. It’s our fault. But it’s also an opportunity for humankind to unite as a species, “the power of 6 billion” as the world’s only superpower, to turn climate change into a success story for Earth and all its rich biodiversity.