Sea Surface temperatures (SST's)
Much is made by IPCC supporters that SST's reinforce the Jones et al land trends.
The facts are that a decade and a half ago Jones et al began adjusting SST's to fit  trends in coastal grd boxes.
Here is a 1992 quote from a prominent climate scientist and IPCC author.
"Moreover, the "observational" records of sea surface temperature actually are affected by urban heating !  What has happened is that Jones and others in the UK adjusted ocean temperatures to coastal values when the two differed."
He goes on to note.  "Without this adjustment, IPCC estimates of global warming over the past century would have been reduced from the relatively small 0.45C + or - 0.15C to the even smaller 0.32C + or - 0.15C -- a trend that isn't much different from zero."

The 1984 paper  Folland, Parker and Kates  Worldwide marine temperature fluctuations 1856-1981, Letter to Nature, Vol 310, 23 Aug 1984, page 670-673.  (FP&K),  shows graphically the huge inhomogeneities in SST raw data.
Raw SST's
The attached Fig 2 out of  FP&K 1984 illustrates uncorrected anomalies in panel above and shows neatly the huge "corrections" required in SST's around WWII.. (Excuse ancient photocopying).    Note in both graphics A is SST trend, B is Nighttime marine air.
With such huge and poorly understood inhomogeneities you could not place great confidence in any trend derived from SST's over the full period of data.
The FK&P original had the graphs broken at 1920, I have spliced them to a continuous trend.
The Corrected anomalies are below. A and B are the same as above.
Corrected SST's
Notice how slight any trend must be over full timescale and how the late 19C is on a par with the warmth of recent times..
Closer to nailing another IPCC lie.
There are early US SST trends by Oort and also Newell which I keep an eye out for.