Chapter 8 examines the IPCC’s claim that CO2-induced increases in air temperature will cause unprecedented plant and animal extinctions, both on land and in the world’s oceans. We find there little real-world evidence in support of such claims and an abundance of counter evidence that suggests ecosystem biodiversity will increase in a warmer and CO2-enriched world.

Chapter 8 Key Findings

• The IPCC claims “new evidence suggests that climate-driven extinctions and range retractions are already widespread” and the “projected impacts on biodiversity are significant and of key relevance, since global losses in biodiversity are irreversible (very high confidence).” These claims are not supported by scientific research.

• The world’s species have proven to be remarkably resilient to climate change. Most wild species are at least one million years old, which means they have all been through hundreds of climate cycles involving temperature changes on par with or greater than those experienced in the twentieth century.

• The four known causes of extinctions are huge asteroids striking the planet, human hunting, human agriculture, and the introduction of alien species (e.g., lamprey eels in the Great Lakes and pigs in Hawaii). None of these causes are connected with either global temperatures or atmospheric CO2 concentrations.

• Real-world data collected by the United Nations Environmental Program (UNEP) show the rate of extinctions at the end of the twentieth century was the lowest since the sixteenth century-despite 150 years of rising world temperatures, growing populations, and industrialization. Many, and probably most, of the world’s species benefited from rising temperatures in the twentieth century.

• As long as the atmosphere’s CO2 concentration rises in tandem with its temperature, most plants will not need to migrate toward cooler conditions, as their physiology will change in ways that make them better adapted to warmer conditions. Plants will likely spread poleward in latitude and upward in elevation at the cold-limited boundaries of their ranges, thanks to longer growing seasons and less frost, while their heat-limited boundaries will probably remain pretty much as they are now or shift only slightly.

• Land animals also tend to migrate poleward and upward, to areas where cold temperatures prevented them from going in the past. They follow earth’s plants, while the heat-limited boundaries of their ranges are often little affected, allowing them to also expand their ranges.

• The persistence of coral reefs through geologic time-when temperatures were as much as 10̊-15̊C warmer than at present, and atmospheric CO2 concentrations were two to seven times higher than they are currently-provides substantive evidence that these marine entities can successfully adapt to a dramatically changing global environment.

• The 18- to 59-cm warming-induced sea-level rise that is predicted for the coming century by the IPCC falls well within the range (2 to 6 mm per year) of typical coral vertical extension rates, which exhibited a modal value of 7 to 8 mm per year during the Holocene and can be more than double that value in certain branching corals. Rising sea levels should therefore present no difficulties for coral reefs.

• The rising CO2 content of the atmosphere may induce very small changes in the well-buffered ocean chemistry (pH) that could slightly reduce coral calcification rates; but potential positive effects of hydrospheric CO2 enrichment may more than compensate for this modest negative phenomenon. Real-world observations indicate that elevated CO2 and elevated temperatures are having a positive effect on most corals.

• Polar bears have survived changes in climate that exceed those that occurred during the twentieth century or are forecast by the IPCC’s computer models.

• Most populations of polar bears are growing, not shrinking, and the biggest influence on polar bear populations is not temperature but hunting by humans, which historically has taken a large toll on polar bear populations.

• Forecasts of dwindling polar bear populations assume trends in sea ice and temperature that are counterfactual, rely on unvalidated computer climate models that are known to be unreliable, and violate most of the principles of scientific forecasting.

Chapter 8. Species Extinction (PDF, 556 kb)

     8.1. Explaining Extinction (PDF, 99 kb)
            8.1.1. Defining Extinction
            8.1.2. Past Extinctions
            8.1.3. Theories of Contemporary Extinctions
            8.1.4. Data on Contemporary Species
            8.1.5. Rapid Evolutionary Change

     8.2. Terrestrial Plants (PDF, 78 kb)

     8.3. Coral Reefs (PDF, 316 kb)
            8.3.1. Indirect Threats
            8.3.2. Direct Threats

     8.4. Polar Bears (PDF, 190 kb)
            8.4.1. Arctic Sea Ice
            8.4.2. Temperatures
            8.4.3. Population
            8.4.4. Forecasts