Keynote speech Global climate change: Challenges and opportunities

May 10, 2011
Ecosystems and Human Health

Dr Nobre introduced the term “Anthropocene ” to describe the most recent period in the Earth’s history, beginning with the Industrial Revolution. “The influence of mankind on the Earth in recent centuries has become so significant as to constitute a new geological era,” Dr Nobre said.

Population is the main driver of this era. “Every hour, 10,000 people join the global population,” and as a result, “every hour, four million tons of carbon dioxide are emitted; 1,500 hectares of forests are cut; and three species go extinct.”

Dr Nobre said damage has been so extensive that “species extinction is unavoidable.” Every Celsius degree of temperature rise above pre-industrial levels is likely to cause the extinction of approximately 10% of species.

“In the past 50 years, we have seen a dramatic degradation of the Earth’s natural capital,” Dr Nobre said. Concentrations of carbon dioxide, nitrous oxide, and methane have risen; land degradation, loss of biodiversity, and water pollution have increased dramatically; observations of atmospheric composition show that all concentrations of greenhouse gases (GHG) are increasing. “Therefore, future warming is unequivocal and already committed.”

The current level of fossil-intensive “business as usual” is resulting in carbon dioxide concentrations in the atmosphere that are “well beyond the [historical] limit,” he said. Computer model charts show rising atmospheric temperature, rising sea levels, and reductions in Northern Hemisphere snow cover.

Studies of specific emission reduction initiatives have evaluated to what extent we can “avoid climate impacts,” said Dr Nobre . If emissions remain constant, global surface warming will increase by 1.8ºC by 2100. Even if emissions cease altogether, global surface warming will increase by 0.6ºC by 2100. We cannot stop climate change but, if we act now, we can mitigate its effects.

If we cut emissions by 50%, the impact of climate change would still be felt in our ecosystems and population health. Health sector impacts could include increased cardiorespiratory and infectious diseases; increased mortality from heat waves, floods, and droughts; and changes to the distribution of some disease vectors.

If 80% of emissions are cut by 2050, with a peak date of 2015, increased amphibian extinction is still likely to occur by 2100. If the peak date is delayed to 2035, 20% to 30% of all species will be at an increasingly high risk of extinction in 2100. “Delaying mitigation is dangerous and costly,” Dr Nobre said.

Reducing emissions requires action across many sectors, including power production (24% of energy emissions), transportation (14%), land use (18% of non-energy emissions), and waste management (3%).

Many options for mitigation exist, said Dr Nobre , noting that policy and price play an important role. Low-cost abatement opportunities include insulation improvements, fuel-efficient commercial vehicles, sugar cane biofuels , and nuclear power.

Dr Nobre addressed the question of whether a developing country can “rise to an acceptable level of human development without overloading its environment.” Developed countries have ecological footprints far in excess of the world average biocapacity available per person, with the sole exception of Cuba. Better models are needed.

“Biofuels and bioenergy are seen as important elements of a multisectoral policy to mitigate climate change,” Dr Nobre said. “However, there are still open questions on bioethanol versus food production, and the synergistic impact of climate change and biofuel production expansion has to be assessed.” Bioethanol expansion also poses threats to biodiversity in Brazil.

Climate change particularly threatens the Amazon, said Dr Nobre . He presented photographs of forest fires, asking “Can we avoid that the Amazon becomes this?” Global climate change will cause 43% of the 69 species of Amazonia angiosperms to become nonviable by 2095. “We need a new model in the tropics,” Dr Nobre said. The traditional model contributed to by soy farms, the timber industry, and ranches, is unsustainable and results in up to 30 square kilometres per year of deforestation, while constituting less than 0.5% of Brazil’s gross domestic product. Dr Nobre noted that 700 square kilometres have already been deforested.

A new paradigm is necessary, said Dr Nobre . Value should be added to the standing forests in developing a new model for the tropics. Small-scale agriculture, water resources, biodiversity, and environmental services could contribute to this new model.

“The global financial crisis is popularizing the concept of systemic risk,” Dr Nobre said. Governments committed more than US$5 trillion to bail out financial institutions out of fear of “ill-defined systemic risk” to the global economy. He compared this to climate change, introducing the concept of systemic risks for Earth systems.

Outlining the impacts at dangerous climate thresholds, Dr Nobre noted that ice in Western Antarctica will be lost at a 0.6ºC rise, tropical Andes ice and late summer Arctic ice will disappear at 1.0ºC, and both the Amazon forest and the oceanic thermohaline circulation will collapse at 4ºC.

Dr Nobre displayed satellite imagery showing dramatic changes in Arctic Ocean ice that have already occurred. “Imagine the Arctic Ocean without ice, a tipping point we very likely have already crossed.” He said another significant tipping point is ocean acidification, the result of carbon absorption by the ocean. “We are mortgaging the planet at sub-prime rates,” he concluded.

Dr Carlos Nobre
Earth System Science Centre
National Institute for Space Research, Brazil

Read Dr. Nobre's blog on climate change at
National Institute for Space Research, Brazil