| 17 | 19 | There have been some concerns that cycle 23 was unusually long and repeating this special cycle would give out of phase behavior of a normal 11-year solar cycle around 2050. Cycle 23 is actually only 12.2 years long not 13 years since it goes from 1996.4 to 2008.6. In Lean and Rind (2009, GRL, doi:2009GL038932) the irradiance was projected forward by just repeating cycle 23. Since it is unknown what the sun will do, there is going to be a lot of uncertainty for future solar irradiance projections. Also the two prior cycles (21 and 22) have been shorter than average - the official times of minima are 1976.5, 1986.8, 1996.4 and now 2008.6 so cycle 21 was only 10.3 years and cycle 22 was 9.6 years - which are not 11 years either! Cycles 21 and 22 have been some of the highest and shortest on record and its quite possible that cycle 23 may be more representative of the future - but of course nobody knows. |
