Original sentence: Other human effects are relevant - for example, sulphate aerosol are believed to lead to cooling - and natural factors also act.Over the past 150 years human activities have released increasing quantities of greenhouse gases into the atmosphere, which theory and climate models say should lead to increases in temperature - colloquially known as global warming.The current best answer is, roughly, most of the warming observed over the last 50 years is attributable to human activities
Edited sentence: Other human effects are relevant - for example, sulphate aerosol are believed to lead to cooling - and natural factors also affect the global climate.Over the past 150 years human activities have released increasing quantities of greenhouse gases into the atmosphere.The extent to which human and natural influences on the climate have changed it is still a matter of debate.The majority of the GHGs have been released since the 1970s though the majority of reported global warming occurred before that