Which of the following statements is true? 1. The Intergovernmental Panel on Climate Change (IPCC) has ruled that all future research use the one computer climate model that it has concluded is the best. 2. The worst-case scenario predicts that if global warming continues at its present rate, by 2050 the average annual temperature will have increased from 15°C to 20°C. 3. Most climate scientists believe that current temperature increases are due entirely to natural cycles of short-term climate changes. 4. Carbon dioxide concentration of the atmosphere has increased in the last century

4.

Explanation:

Option number 4 is true out of all the options provided.

1. The Intergovernmental Panel on Climate Change (IPCC) has not ruled that all future research use the one computer climate model, and they have not concluded that it is the best.

2. The worst-case scenario predicts that global warming will increase the average temperature by 1.5°C - 2°C. Not from 15°C to 20°C.

3. Very few climate scientists believe that current temperature increases are due to natural cycles of short-term climate changes.

4. Over the past century, there has been an increase in industrial work, car and truck emissions, and the population of humans have increased dramatically. Add that to deforestation and there is a clear explanation as to why there has been an increase in the concentration of carbon dioxide in the air.