The puzzle of renewed growth in atmospheric methane concentrations: engaging with interdisciplinary networks and raising awareness

Methane is a greenhouse gas that is emitted from diverse human and natural sources that include fossil-fuel activities, agriculture, wetlands, and fire. Since the industrial revolution, atmospheric concentrations of methane have increased by more than 150% and methane is now the second leading greenhouse gas after carbon dioxide. Given the shorter lifetime of methane in the atmosphere, combined with a more potent radiative forcing than carbon dioxide, and its role in reactive chemistry and tropospheric ozone formation, methane is under intense scrutiny. Despite this, the decadal scale dynamics of the growth of methane in the atmosphere has proven challenging to fully understand. For example, from 1999-2006, methane concentrations remained stable in the atmosphere, but in 2007, the growth of methane rose abruptly and has continued to increase through 2018. Both the period of stabilization and the period of renewed growth remain unexplained because of the complexity of emission sources, their transport in the atmosphere, and their removal by chemical 'sinks'. A wide variety of efforts have taken place to both integrate the science needed to explain the recent growth of methane and to also raise the awareness with the public and with policy-makers. These efforts range from national synthesis activities, i.e., North American Carbon Program, to international consortia, i.e., the Global Carbon Project and its Global Methane Budget. The activities require researchers to communicate their sub-disciplines in a common currency to assemble budgets of methane that aim to balance, and where the imbalance suggests areas for further research. This presentation discusses how partnerships between scientists and engagement using various science communication strategies have contributed to an improved awareness of the renewed growth in atmospheric methane concentrations.