Sea levels have been rising naturally for the past 20,000 years since the peak of the last ice age, and at much, much faster rates in the past (up to 40 times faster than today). Sea level rise greatly decelerated about 8,000 years ago to rates similar to today:
Sea levels are currently rising 4 to 8 inches per century, and there is no acceleration, which means there is no evidence of a human influence on sea levels.
References finding either no acceleration or a deceleration of sea level rise during the 20th and 21st centuries:
JM Gregory et al Journal of Climate 2012
Dean & Houston 2011 & 2013
Scafetta 2013
Holgate 2007
Boretti 2012
Morner 2004
Jevrejeva et al 2006 & 2008
Wöppelmann et al 2009
Roemmich et al 2013
IPCC 2007:
“no long-term acceleration of sea level has been identified using 20th-century data alone.”
IPCC 2013:
“It is likely that GMSL [Global Mean Sea Level] rose between 1920 and 1950 at a rate comparable to that observed between 1993 and 2010”