Here’s a fresh look at global temperatures as calculated by the University of Alabama, Huntsville- the UAH dataset– from satellite measurements of the Temperature of the Lower Troposphere (TLT).
Warwick Hughes suggests that there has been a drift in the measurements since about 2005, such that calculated temperatures are too high, and we await a proposed correction. However, we can live with that.
Here are plots of TLT for various regions of the globe.
Fig.1: 12 month running means of Global anomalies and Tropical anomalies (the region of the Earth between 20 degrees North and 20 South, which gets the majority of the solar radiation striking the Earth).
The two sets move in lock step, with a much larger variation in the Tropics than the world as a whole.
What causes these large variations?
SOI is the acronym for the Southern Oscillation Index, calculated from pressure differences between Tahiti and Darwin, and is a reasonably good indicator of El Nino or La Nina conditions. The ENSO cycle (El Nino Southern Oscillation) originates in the tropical Pacific. El Nino brings warmer temperatures to the world; La Nina is associated with cooler temperatures. I have inverted the SOI to show this relationship, and scaled it down by 30 to fit on the graph.
Note how the 12 month mean of SOI precedes the temperature data. Here’s a plot with the SOI advanced 5 months.
While the peaks (El Ninos) match very closely, I have marked periods following the major eruptions of El Chichon and Mt Pinatubo, which cooled temperatures for several years. I also suggest that the atmospheric dust and cooler surfaces upset the ENSO cycle as traced by the SOI. Note also that temperatures in the 2010-2011 La Nina appear higher than expected.
Note how Australian temperatures appear to fluctuate about as much as the Tropics (we’re one third north of 20S after all). Australian temperatures are influenced by events in the Indian Ocean and Southern Ocean as well as the Pacific, so the match isn’t exact.
I will look at Australian data specifically in another post.
Finally, here’s a way to check on that other “finger print” of the enhanced greenhouse effect, as espoused by Dr Karl Braganza: land areas are expected to warm faster than oceans, supposedly showing that greenhouse gases, not ocean currents, drive global warming.
Well of course that proves it- land areas are indeed warming faster than oceans.
However, have a closer look at the timing of the switches between warming and cooling. If well mixed greenhouse gases are warming both land and oceans, it would be expected that oceans, with higher specific heat and enormous thermal inertia, would take longer to warm. The land response would be almost immediate. Oceans would not be expected to warm before the land, and if anything might show a slight lag.
The oceans change phase about one month before the land. They definitely do not lag behind.
And what causes these rapid changes?
The world’s temperatures respond to the powerful beat of ENSO events- as well as large explosive volcanic