For RSS TTT (troposphere), the 12 months to May 2017 is the second the hottest 12 months in the record (comparing similar June-May periods). Now that last year's intense El Nino has dissipated, May itself was the just the fourth hottest May, with May 2016 the hottest.
The lower troposphere (UAH v6) also showed the 12 months to May as the second hottest on record. However, in the UAH record, May was the third hottest May on record, after May 1998 and May 2016.
Troposphere temperature (RSS TTT v4) chart
First here is RSS TTT with the latest dataset, version 4. TTT seems to measure more of the troposphere than TLT (that is, it has a greater vertical profile) with less of the stratosphere than the mid-troposphere data (TMT). It shows a higher rate of warming than RSS v3.3 and higher than UAH. Hover the cursor (arrow) over the plots to see the data points, trend etc.
The chart below is the average of the 12 months to May each year from 1979 through to 2017. The annual averaged anomaly was 0.63 °C, which is 0.09 °C lower than the previous hottest 12 month June-May period that ended in May 2016. The rate of warming is 0.18 °C/decade or 1.8 °C/century.
From the RSS website, TTT is derived from TMT and TLS with the formula:
TTT = 1.1*TMT - 0.1*TLS.
This combination reduces the influence of the lower stratosphere, which is cooling at most locations. TLT gives most weight to the temperatures closer to the surface. TTT gives more weight to the troposphere and less to the stratosphere than TMT does, but not as much to the lowest levels of the troposphere as TLT does. However TTT has version 4, while TLT is still only provided as version 3.3. For a fuller explanation see the RSS website or the July 16 report here.
Below is the TTT chart just for the month of May. The anomaly for May was 0.608 °C, which is 0.133 °C cooler than May 1998. The rate of warming just for the month of May is 0.16 °C/decade.
The rest of the charts are from UAH v6. This is almost identical to the old version of RSS, which is v3.3, so I don't regard it as being as good as RSS TTT v4.
The chart below is the average for each 12 month period ending in May each year (1979 to 2017). The 12 months to May 2017 is 0.35 °C, which is the second hottest June-May period on record, 0.11 °C lower than the 12 months ending in May 2016.
Below is the UAH chart for the month of May only for each year going back to 1979. The anomaly was 0.45 °C above the 1981-2010 mean, which was the third warmest May in the record, and 0.19 °C cooler than the hottest May in 1998.