But it will also make history as marking a new era of climate change reality with record high greenhouse gas concentrations." The report also details the growth in other greenhouse gases, including methane and nitrous oxide. In 2015, levels of methane were 2.5 times greater than in the pre-industrial era, while nitrous oxide was 1.2 times above the historic measure. The study also points to the impact of these increased concentrations of warming gases on the world's climate. Between 1990 and 2015 there was a 37% increase in radiative forcing or warming effect, caused by a build up of these substances, from industrial, agricultural and domestic activities. While welcoming new initiatives like the global agreement to phase out HFC gases agreed recently in Rwanda, the WMO argues that nations must retain their focus on cutting CO2. "Without tackling CO2 emissions, we cannot tackle climate change and keep temperature increases to below 2 degrees C above the pre-industrial era," said Petteri Taalas. "It is therefore of the utmost importance that the Paris Agreement does indeed enter into force well ahead of schedule on 4 November and that we fast-track its implementation." Around 200 nations who signed the Paris climate agreement will meet in Morocco in November to decide on the next steps forward.