News: the RSS AMSU data for April 2010 are out. The anomaly, 0.546, is the lowest one for 2010 so far. It is the second warmest April on their record but it's more than 0.3 °C cooler than April 1998 and April 2005 was just a bit cooler than April 2010.
Originally posted on May 1st
When you look at the daily UAH AMSU temperatures for April 2009 and April 2010, you will find out that the near-surface average brightness temperature for April 2010, -15.50 °C, was 0.4 °C warmer than that of April 2009, which was -15.90 °C.
That's a substantial year-on-year warming. However, with the anomaly around 0.55 °C using these centidegree conventions, as well as with the anomaly around 0.48 °C using these millidegree conventions, April 2009 will be the coolest month of 2010 so far.
It will be calculated to be the second warmest April on the UAH record, after April 1998 which remains the hottest month since 1978 when the UAH records began (and probably for a few centuries, too). The UAH anomaly in April 1998 was 0.76 or 0.77 °C, respectively, so the April 2010 anomaly will still be a whopping 0.2 or 0.3 °C cooler than April 1998.
The El Nino has weakened but the El Nino conditions continue and will continue through the summer. The year 2010 is likely to end up pretty close to 1998, the warmest year on the UAH record so far.
Note: the daily data contain some systematic error - because they use a "wrong" satellite - so they're not the best ones that the UAH team uses for their official figures now. But they're the best data that are instantly available on the daily basis. Sorry for the mess with the multiple datasets, it's not my fault. Because of these and various errors and confusions, my estimates must be understood as figures with a 0.05 °C error margin.