Why has the European Union called for dramatic cuts in carbon dioxide and greenhouse gas emissions?

Q. A new analysis has determined that the threat of global warming can still be greatly diminished if nations cut emissions of heat-trapping green-house gases by 70% this century. The analysis was done by scientists at the National Centre for Atmospheric Research (NCAR). While global temperatures would rise, the most dangerous potential aspects of climate change, including massive losses of Arctic sea ice and permafrost and significant sea-level rise, could be partially avoided.
“This research indicates that we can no longer avoid significant warming during this century,” said NCAR scientist Warren Washington, the study paper’s lead author. “But, if the world were to implement this level of emission cuts, we could stabilise the threat of climate change”, he added.
Average global temperatures have warmed by close to 1°C since the pre-industrial era. Much of the warming is due to human-produced emissions of greenhouse gases, predominantly carbon dioxide. This heat-trapping gas has increased from a pre-industrial level of about 284 parts per million (ppm) in the atmosphere to more than 380 ppm today. With research showing that additional warming of about 1°C may be the threshold for dangerous climate change, the European Union has called for dramatic cuts in emissions of carbon dioxide and other greenhouse gases.
To examine the impact of such cuts on the world’s climate, Washington and his colleagues ran a series of global studies with the NCAR-based Community Climate System Model (CCSM). They assumed that carbon dioxide levels could be held to 450 ppm at the end of this century. In contrast, emissions are now on track to reach about 750 ppm by 2100 if unchecked. The team’s results showed that if carbon dioxide were held to 450 ppm, global temperatures would increase by 0.6°C above current readings by the end of the century. In contrast, the study showed that temperatures would rise by almost four times that amount, to 2.2°C above current readings, if emissions were allowed to continue on their present course. Holding carbon dioxide levels to 450 ppm would have other impacts, according to the climate modeling study.
Sea-level rise due to thermal expansion as water temperatures warmed would be 14 cm (about 5.5 inches) instead of 22 cm (8.7 inches). Also, Arctic ice in the summertime would shrink by about a quarter in volume and stabilize by 2100, as opposed to shrinking at least three-quarters and continuing to melt, and Arctic warming would be reduced by almost half.

Why has the European Union called for dramatic cuts in carbon dioxide and green-house gas emissions?

Q. Carbon dioxide is one of the greenhouse gases and an increase in the carbon dioxide content in the atmosphere would cause more heat to be retained by the atmosphere and lead to global warming.

Q. Which of the following options are correct regarding given assertion and reason?

Assertion [A] : An increase in carbon dioxide in the atmosphere leads to global warming.

Reason [R] : Carbon dioxide is a greenhouse gas.

Q. State true or false.
Carbon dioxide is one of the greenhouse gases and an increase in the carbon dioxide content in the atmosphere would cause more heat to be retained by the atmosphere and lead to global warming.

Q.  Which of the following statement(s) given below is/are correct?

1. Nitrous oxide, released by chemical fertilizers and burning of fossil fuels, has a higher global warming potential than that of carbon dioxide
2. Carbon dioxide is the Greenhouse gas that contributes most to climate change