So, overall.... We have some good satellite data, dedicated resources in use, and the ability to track changes over time with pretty good resolution and frequency. We would be able to "see" an underwater volcanic eruption of a fairly small scale with observing an anomalous "hot spot" where a convection current brings the heat to the surface. We have virtually no instruments in place for tracking deep sea temps, particularly below 300m depth. We have absolutely no instruments in place for tracking changes in deep well earth temps or heat flux. We have no clue about changes in carbon dioxide concentrations in the oceans, where most of our "free" carbon exists. summary..... we just don't know what the hell is happening to our planet, really. Or to our climate. But there are a lot of hot head trendy charlatans predicting doom, claiming we gotta change our political and economic civilization and go to hell like Venezuela.