Ian Plimer

Heaven and Earth

The IPCC has promoted the view that global warming creates extinction. This was based on one study. Suggestions that human-induced global warming results in extinction is, at best, scientifically flawed. It was suggested that rising sea surface temperature in the equatorial Pacific Ocean led to the disappearance of 22 of the 50 known species of frogs and toads in the Montverde cloud forest of Costa Rica. However, the authors also suggested that lowland deforestation may have a major influence on preservation of the cloud forests. This reservation was ignored as human-induced global warming was given as the reason for extinction. Although 21 of these species are known from elsewhere, one species (the golden toad) lost its only habitat and became extinct. It was the loss of this species that led to the conclusion that human-induced global warming could create an extinction of 20% of species over 50 years with a 0.8°C temperature rise. However, the trade winds that bring moist air from the Caribbean spend 5 to 10 hours over lowlands before they reached the golden toad's habitat. By 1992, 18% of the lowland vegetation remained after land clearing, resulting in an increase in the altitude of the cloud base thereby depriving the cloud forests of their moisture. Land clearing created the extinction of the golden toad, not global warming.

Estimates of the impact of climate change on wildlife using the modelling method endorsed by the IPCC ate a good example. When the models are run, they are not in accord with the modern distribution of wildlife. This agrees with other studies on the effect of climate change on wildlife. They are worthless because, despite the advances in mathematical simulation, the assumptions made are simplistic and lack critical variables. The scope for error is huge and cannot be reliably estimated. The same models have warned us that there will be massive extinction if the temperature rises yet these predictions of extinction arc the opposite of what is seen with past warmings. A consultation with the Oracle at Delphi would be a more useful method of prediction.

Other emotive speculations on extinction are misleading, such as those regarding foxes in the Arctic, as touted by the IPCC. The key publication on foxes does not deal with extinction but migration of red foxes into the range of Arctic foxes in North America and Eurasia. The Arctic foxes survived the last interglacial warming and the Roman and Medieval Warmings and hence it is hardly likely that the milder Late 20th Century Warming would lead to their extinction. There are a great diversity of reasons for species migration which seem to be related to hunting or competition rather than human-induced global warming.

The emotion about human-induced global warming is underpinned by the assumption that a future climate change will be so rapid that plants and animals would not be able to adapt to with the rate of temperature change. This view ignores the past, where there have been large climate changes on the scale of decades which have not led to plant or animal extinction. For example, the Fremont Glacier in Wyoming records a substantial warming from 1840 to 1850. A substantial warming in less than a decade is far faster than the most speculative catastrophist models for human-induced global warming, yet there is no evidence that there was an extinction in North America at that time. Multicellular plants and animals have been on Earth at least 500 million years, so they have enjoyed at least 20 major climate changes. If we took the emotive argument to its logical conclusion, then there would be no multicellular life on Earth, as previous global warmings would have tendered life extinct and planet Earth would be a moonscape. Why was there not an extinction with the Eemian interglacial, the Younger Dryas, the Roman Warming, the Dark Ages, the Medieval Warming or the Little Ice Age? Why is it that only the Late 20th Century Warming will produce extinction whereas previous times when it was far warmer did not produce an extinction?

A key argument is that plants are immobile, hence a rapid global warming will push them into extinction. The scenario is that when plants become extinct, then animals that feed off plants will also become extinct. Because this was not seen in previous warmings, the alarm bells should have been ringing for those speculating about extinction due to warming. What is observed is that plants in the Arctic have adapted to the frigid conditions but their distribution is rarely limited by warm conditions. Many Arctic and alpine plants are extremely tolerant to high temperatures, adult trees harvest the light and it is only when an adult tree dies that a plant is replaced. This process takes time thereby giving lichen, fungi and animals time to move with the migrating plant ecosystem.

Geology shows that in times of global warming, there is an explosion of life, diversity increases and speciation is rapid. The Cambrian explosion of life (542-520 Ma) took place in the post-glacial warm times when atmospheric CO₂ was at least 25 times greater than today. Other great diversifications have taken place in the past. Species-rich forests existed during the warm Tertiary times in the western USA where many mountain species grew amongst mixed conifers and broad leaf sclerophylls. It is only by completely ignoring the history of the planet can it be claimed that global warming can produce extinction.

In modern settings, it is also suggested that increased temperature will bring more species diversity by extending the ranges of plants and animals. Replacement of high altitude forests by mixing with low altitude forests to create greater species diversity has happened in previous times of warming and would be expected in another warming event. Furthermore, if a future warmer climate had a higher atmospheric CO₂ content, plant life would be far more vigorous because increased CO₂ enables plants to grow better in nearly all temperatures, especially at higher temperatures. Both animals and plants are limited by the latitude and altitude cold-boundaries of their range and are not limited by the heat-limited boundaries of their range. If atmospheric CO₂ is doubled, plant growth is unaffected at 10°C and growth is doubled at 38°C.

On a global scale, satellite measurements of vegetation between 1982 and 1999 showed that plant growth increased by 6% in response to slightly increased rainfall, and slightly increased temperature but the major change was due to slightly increased CO₂. If the CO₂ content is doubled, the net productivity rise of herbaceous plants is 30 to 50%, while of woody plants it is 50 to 80%. In the European Alps, there are plant species counts from 1895 to the present. Mountaintop temperatures have increased by 2°C since 1920 with 1.2°C of that rise over the last 30 years. Of the 30 mountaintops, nine showed no change in the species count, 11 gained 59% more species and one had a 143% increase in species. The 30 mountaintops showed a mean species loss of 0.68 out of an average of 15.57 species. The loss of a species from a particular mountain does not mean extinction but shows local mobility of plants. There are numerous other studies of lichen, plants) butterflies, birds, plankton, marine systems and fish to show that a slight temperature rise induces species diversity species migration and adaptation.

These observations show that planet Earth is dynamic. Life is constantly adapting to change. Life will adapt to change when temperature and atmospheric CO₂ rise slightly. Whether the changes are natural or human-induced is irrelevant. Far greater changes occurred in pre-industrial times without extinction of life. Detailed studies in a specific area may record a local extinction. However, this is misleading, as an extinction is the total loss of a species whereas local extinction could mean that a species has migrated to another area. Some species that were thought to be extinct in one area have been found decades later in another area.

To argue that increasing temperature and atmospheric CO₂ will result in extinction of plants is to argue that CO₂ is not plant food. Even if the planet warms due to increased atmospheric CO₂ it is clear that plants will not feel the need to migrate to cooler parts of our planet. In fact it is the very opposite. Young plants adsorb more CO₂ than old plants. If we wanted an effective carbon plant sequestration scheme, then we would cut down all our old growth forests and plant saplings or even leave what was forest as grass, both of which would adsorb far more CO₂ than mature trees.