Taking the pulse of the planet

Here we explore better ways of measuring global warming to answer these questions. Natural temperature variability is much more muted in the ocean than in the atmosphere, owing to the ocean's greater ability to absorb heat (its heat capacity). As a result, ocean heating and sea level rise, which are measured independently, show stronger evidence that the planet is warming than does global average surface temperature, which relies on air temperature measurements.

In other words, these ocean measurements could provide vital signs for the health of the planet. Thus, we suggest that scientists and modelers who seek global warming signals should track how much heat the ocean is storing at any given time, termed global ocean heat content (OHC), as well as sea level rise (SLR). Similar to SLR, OHC has a very high signal-to-noise ratio; that is, it clearly shows the effects of climate change distinct from natural variability.