Over the past 30 years, global temperatures have risen continuously by around 0.2°C per decade; the ten warmest years on record have occurred since 1990.1 Since the discovery of this trend, there has been considerable debate over whether climate change can be attributed to human activities. Although arguments are made against human induced climate change,2 most scientists nowadays ascribe global warming to an increase in greenhouse gases (GHG) caused by human activities.3 To tackle global warming, the United Nations (UN) developed a global