Global warming behind mass animal extinctions: Study

NEW DELHI: Scientists have unearthed evidence pointing to a strong relationship between the magnitude of mass animal extinctions and global temperature changes and the study by experts indicate that the bigger the shifts in climate, the larger the mass extinction. 

The study by scientists from the Department of Earth Science, Tohoku University, Japan published in a peer reviewed journal said major mass extinctions in the Phanerozoic Eon (covering 539 million years to the present) occurred during abrupt global climate changes accompanied by environmental destruction driven by large volcanic eruptions and projectile impacts.

The relationships between land temperature anomalies and terrestrial animal extinctions, as well as the difference in response between marine and terrestrial animals to abrupt climate changes in the Phanerozoic, have not been quantitatively evaluated yet. 

“The loss of more than 35 per cent of marine genera and 60 percent of marine species corresponding to the so-called ‘big five’ major mass extinctions correlates with an over 7 degree Celsius global cooling and a 7-9 degree C global warming for marine,” said the study. 

Global cooling and warming have been reported in many periods in the Phanerozoic based on oxygen isotopes. However, most of them are long-term climate changes. Major mass extinctions of animals have occurred five times: 444, 372, 252, 201 and 66 million years ago. 

“The significant relationship between the surface temperature anomaly and extinction magnitude indicates that the cause of major extinctions is surface temperature change and coincidental environmental changes, such as acid rain, ozone depletion, reducing sunlight, desertification, soil erosion, and oceanic anoxia, driven by large volcanic eruptions and projectile impacts,” it added. 

These climatic and environmental anomalies are controlled by stratospheric aerosols, such as sulfuric acid and black carbon, for reducing sunlight - global cooling - and acid rain, halogen for ozone depletion, and atmospheric greenhouse gases, such as CO2 and methene, for surface warming.