Increases in rice and cattle cultivation have lead to large increases in methane gases. Research shows no significant changes in natural activities such as volcano eruptions that would impact GHGs. Watson presents some of the IPCCs modeling on future scenarios. Key determinants include population growth, economic growth, changes in technology and changes in how governments approach the issue. IPCC modeling shows a range of plausible outcomes over the next 50 years, from similar levels as today to dramatic and destructive increases.
More models show the potential impacts on health and agriculture.