求翻译：气候科学家们表示全球必须停止增加温室气体排放，并且在2015到2020年间开始减少排放。科学家们预计想要防止全球平均气温再上升2℃，到2050年，全球的温室气体减排量需达到1990年水平的80%。是什么意思？

Climate scientists say the world must stop the increase in greenhouse gas emissions and begin to reduce emissions in the years 2015-2020. The scientists expect to want to prevent the average global temperature rose further by 2 ° C, global greenhouse gas emission reductions required to achieve 80% o

Climate scientists have said that the global need to stop an increase in greenhouse gas emissions in 2015, and in 2020 began to reduce emissions. Scientists who did it is expected that you want to prevent global average temperatures will rise by up to 2 ° C, to the Year 2050, the global greenhouse g

Climate scientists have said the world must stop the increase of greenhouse gas emissions, and start reducing emissions between 2015-2020. Scientists are expected to wa