Recently Gavin Schmidt tweeted out the figure below, which is a nice way to see the trend associated with global warming in context of the seasonal cycle. It might seem odd that there is a seasonal cycle of global mean temperature, but this is simply due to the fact that there is a lot of dry land in the Northern Hemisphere and a lot of open ocean in the Southern Hemisphere.
This plot also nicely shows how exceptional 2015-2016 has been. This is obviously strongly related to the recent El Niño, but without the warming trend, there would definitely be less temperature records being broken.
In spite of all these records being broken people are still arguing that there is no reason to be alarmed on the WattsUpWithThat blog, based on the comparison to 1998 temperatures in satellite data. However, satellite estimates are not what we use to determine whether the global temperature is exceptional. They are not comparing apples to apples. The lower tropospheric temperature generally tracks the surface temperature pretty well, but it’s still not a direct measurement, so it’s not really a better “ground truth”.
I took a quick look at what people are saying in the comments of that post on WattsUpWithThat, and many of them were mentioning how most station data is in urban areas and is therefore corrupted by the heat island effect. There was also some comments about a NASA conspiracy, but I don’t see any reason to take that concern seriously. To ease anyone’s concern about the land surface station data, all they need to do is look at the measurements over ocean, from buoys, ships, and even satellites. The warming is there!
How do we get people to realize the data is not corrupt!?