The Scripps Oceanographic Institute reports that “On May 9, 2013 the daily mean concentration of carbon dioxide in the atmosphere of Mauna Loa, Hawaii, surpassed 400 parts per million (ppm) for the first time since measurements began in 1958.”  

Keeping CO₂ levels beneath 400 ppm was regarded as essential to confining global warming to two degrees Celsius, which many scientists believe is the ceiling beyond which climate change will become widespread and entail severe impacts.

Accordingly, reaching this threshold marks a new high in human impacts on the planetary environment: Carbon dioxide (CO₂) is the leading greenhouse gas (GHG) and its presence in the atmosphere has been increasing since measurement began. The rise in CO₂ levels is due to the increase in the use of fossil fuels – gas, coal, oil –by industry and for transportation. The fossil record suggests that the atmosphere has not known such levels of CO₂ in at least three million years.

That goal of containing global warming to two degrees may now be out of reach as a result of breaking the 400 ppm threshold. Significantly, many scientists  believe that even this level of CO₂ is excessive since “two degrees [of temperature rise] is actually too much for ecosystems,” according to Thomas Lovejoy, a leading expert in biodiversity, writing in The New York Times last January.  

Long-Term Effects

What are the long-term effects that the CO₂ increase portends? The question is no longer hypothetical. According to NASA, the US National Aeronautics and Space Administration,

Global climate change has already had observable effects on the environment. Glaciers have shrunk, ice on rivers and lakes is breaking up earlier, plant and animal ranges have shifted and trees are flowering sooner.

Effects that scientists had predicted in the past would result from global climate change are now occurring: loss of sea ice, accelerated sea level rise and longer, more intense heat waves.

NASA, based on findings of the Intergovernmental Panel on Climate Change (IPCC), anticipates the following future effects of global warming:

Implications

In terms of health effects alone, the IPCC writes: “Evidence has grown that climate change already contributes to the global burden of disease and premature deaths. Climate change plays an important role in the spatial and temporal distribution of malaria, dengue, tick-borne diseases, cholera and other diarrheal diseases; is affecting the seasonal distribution and concentrations of some allergenic pollen species; and has increased heat-related mortality.”

With respect to  food, the Commission on Sustainable Agriculture and Climate Change reports that “Food insecurity and climate change are already inhibiting human well-being and economic growth throughout the world and these problems are poised to accelerate.” Changing crop patterns, shifts in plant and animal ranges, and fluctuations from the norm in precipitation and water supplies are among the factors that will lead to rising food insecurity, especially in Africa and other developing areas.

Human settlement is concentrated in many coastal areas and sea level rise and inundations affecting islands, delta and other low-lying areas are already manifesting themselves. 

Species loss and habitat disruption and ecosystem failure, for example in the polar region and reef systems, are also of growing concern. Damage to fisheries have already become evident as acidification and warming of the oceans takes place.

Economic Costs

The economic costs of adapting to climate change, mitigating the effects of these changes and funding relief, recovery and rehabilitation efforts due to an increase in the number of disasters and extreme weather events are likely to be overwhelming.

Climate change driven by GHGs is among one of the several engines that are altering not only society but the physical planet as well. Prominent geologists and other earth scientists are now pushing for the formalization of the term anthropocene as a unit of the Geological Time Scale marking the fundamental modifications of the planet that have taken place since the Industrial Revolution two hundred years ago. Most of that change has occurred in the last several decades.

Beyond Awareness to Decisive Action

Awareness of the perils of climate change  is nearly universal in the scientific community with even former skeptics endorsing this consensus. Many if not most policy makers have accepted this consensus. However, international leaders, particularly those of the chief  CO₂ emitters, the US and China,have not committed to taking the necessary steps to roll back the greenhouse gases time bomb.

At 440 ppm of atmospheric CO_2, the clock is ticking. Opportunities to avoid severe impacts will decrease the more we wait.