Over the last decade the number of paleoceanographic studies presenting and
discussing alkenone-derived sea surface temperature (SST) records and carb
on isotope ratios of alkenones (delta C-13(alkenones)) has increased rapidl
y. This short review paper summarizes the state of knowledge about SST vari
ability determined by alkenone paleothermometry in sediment trap studies an
d investigations of marine sediments for timescales of single to millions o
f years. In particular from the evaluation of Quaternary records, character
istic temperature pattern have emerged that mismatch with SST curves estima
ted by other methods, e.g., foraminiferal stable oxygen isotopes and transf
er functions. In future studies the spatial distribution of such variance p
atterns typically observed in alkenone SST curves should be checked in orde
r to better understand their meaning for ocean circulation changes and a po
ssible relationship to global climate change. On the other hand, certain ph
ysical and biological processes have the potential to put the reliability o
f alkenone SST curves into question. Accordingly, examples for possible eff
ects of bioturbational mixing, lateral transport of remote alkenones, diagn
etic alteration and degradation of alkenone composition, biogeographic and
temporal diversity changes in alkenone-producing algae, as well as the infl
uence of changes in salinity and nutrient conditions on the alkenone paleot
emperature signal, are briefly mentioned, highlighting the need for more de
tailed future studies on these issues. Finally, a short summary on the stat
us of the use of the delta C-13(alkenones) signal as a proxy for past varia
tions in the carbon dioxide pressure (PCO2) in ocean surface waters and rel
ated problems is given.