Improving Estimates of Earth's Energy Imbalance

Earth is gaining energy owing to increasing greenhouse gas concentrations and the ocean’s large thermal inertia. This energy gain, an essential diagnostic of global warming and attendant sea level rise, is difficult to measure directly, being the small difference of absorbed incoming solar radiation and thermal infrared radiation emitted to space. With over 90% of this energy gain warming the oceans, the most accurate way to quantify it is to measure increases in ocean temperatures (along with the smaller contributions from other parts of the climate system). In 2005 the international global Argo array of autonomous robotic profiling floats first achieved sparse near-global coverage of the upper half of the ocean volume. Combining the heat uptake in the upper half of the ocean volume from 2005 through 2015 from Argo with previously published estimates of heat uptake trends in other parts of the climate system, mostly the deep ocean, allows an estimate of the total heat uptake rate for Earth’s climate system over that decade. This rate anchors a satellite-observed estimate from the Clouds and the Earth’s Radiant Energy System (CERES), which requires an in situ baseline. Year-to-year variations of upper ocean heat uptake and CERES energy imbalance are well correlated during this time. This agreement between two completely independent and complementary measures of Earth’s energy imbalance bolsters confidence in each.  The next biggest (and growing) term and uncertainty in the global energy imbalance is deep ocean warming. Measurements there could be improved by implementing Deep Argo