Question:
Who was the head of Hamburg in Jan, 2011?

Context:
 Klaus von Dohnanyi is the head of the government of Hamburg from Jun, 1981 to Jun, 1988. 
 Olaf Scholz is the head of the government of Hamburg from Mar, 2011 to Mar, 2018. 
 Peter Tschentscher is the head of the government of Hamburg from Mar, 2018 to Dec, 2022. 
 Hans-Ulrich Klose is the head of the government of Hamburg from Nov, 1974 to May, 1981. 
 Henning Voscherau is the head of the government of Hamburg from Jun, 1988 to Oct, 1997. 
 Rudolf Petersen is the head of the government of Hamburg from May, 1945 to Nov, 1946. 
 Paul Nevermann is the head of the government of Hamburg from Jan, 1961 to Jun, 1965. 
 Carl Vincent Krogmann is the head of the government of Hamburg from Mar, 1933 to May, 1945. 
 Peter Schulz is the head of the government of Hamburg from Jun, 1971 to Nov, 1974. 
 Herbert Weichmann is the head of the government of Hamburg from Jun, 1965 to Jun, 1971. 
 Max Brauer is the head of the government of Hamburg from Nov, 1946 to Dec, 1953. 
 Christoph Ahlhaus is the head of the government of Hamburg from Aug, 2010 to Mar, 2011. 
 Ortwin Runde is the head of the government of Hamburg from Nov, 1997 to Oct, 2001. 
 Ole von Beust is the head of the government of Hamburg from Oct, 2001 to Aug, 2010. 
 Kurt Sieveking is the head of the government of Hamburg from Dec, 1953 to Nov, 1957.

Answer:
Christoph Ahlhaus