DOI: 10.3886/e233281v1
title: Climate.gov Data Snapshots: SST - Global, Monthly Difference from Average

description: <b>Q: Is sea surface temperature warmer or cooler than usual?
</b><b>
 </b><br><b>A:</b> Colors
 on this map show where and by how much monthly sea surface temperature 
differed from a long-term average (1985-1993, details from Coral Reef Watch).
 Red and orange areas were warmer than average, and blue areas were 
cooler than average. The darker the color, the larger the difference 
from the long-term average. White and very light areas were near 
average.

 
 <br><b>Q: Where do these measurements come from?
</b><b>
 </b><br><b>A:</b> These monthly measurements are made from NOAA's CoralTemp sea
 surface temperature (SST) data. Every day, instruments on eight 
satellites in two different orbits (geostationary and polar) measure sea
 surface temperature by checking how much energy is radiated by the 
ocean at different wavelengths. Computer programs plot these 
measurements on a gridded map and then merge and smooth the data into a 
gap-free product using mathematical filters. Each grid point covers an 
area approximately 5 x 5 km. Daily temperatures at each grid point are 
averaged together to calculate monthly average temperature. 

To calculate the difference-from-average temperatures shown here, a 
computer program takes the monthly average temperature at each grid 
point, and subtracts the long-term average for that month. If the result
 is a positive number, the sea surface was warmer than the long-term 
average. A negative result from the subtraction means the sea surface 
was cooler than usual.

 
 <br><b>Q: What do the colors mean?</b><b>
 </b><br><b>A: </b>Shades
 of blue show locations where sea surface temperature was cooler than 
its long-term average. Locations shown in shades of orange and red are 
where the sea’s surface was warmer than the long-term average. The 
darker the shade of red or blue, the larger the difference from the 
long-term average or “usual” sea surface temperature. Locations that are
 white or very light show where sea surface temperature was the same as 
or very close to its long-term average.

 
 <br><b>Q: Why do these data matter?</b><b>
 </b><br><b>A:</b> Water
 covers more than 70% of our planet's surface. Tracking the temperature 
of the sea’s surface helps scientists understand how much heat energy is
 in the ocean and how it changes over time. Sea surface temperatures can
 have dramatic impacts on weather, including weather patterns such as El
 Niño-Southern Oscillation (ENSO) that travel hundreds of miles inland. 
Sea surface temperatures also play a significant role in the extent and 
thickness of Arctic and Antarctic sea ice, which serve as our planet’s 
built-in air-conditioning system. And sea surface temperatures have 
significant effects on marine life. The upwelling of cold water, for 
instance, provides nutrients to phytoplankton, the base of the marine 
food chain. In contrast, warm ocean surface waters deprive phytoplankton
 of nutrients, sometimes with devastating effects up the chain.

 
 <br><b>Q: How did you produce these snapshots?</b><b>
 </b><br><b>A:</b> Data
 Snapshots are derivatives of existing data products: to meet the needs 
of a broad audience, we present the source data in a simplified visual 
style. NOAA's Environmental Visualization Laboratory (NNVL) produces the
 Sea Surface Temperature Anomaly files. To produce our images, we run a 
set of scripts that access these NNVL source files, re-project them into
 a Hammer-Aitoff globe, and output them in a range of sizes.

 
 
 
 <br><b>References</b>
 
 NOAA NNVL Sea Surface Temperature Anomaly (SSTA)<br>
NOAA NNVL SSTA FTP access<br>
NOAA Coral Reef Watch<br>
CoralTemp data<br>
CoralTemp climatology (long-term average)<br>
CoralTemp climatology methodology
 <br>Source: https://www.climate.gov/maps-data/data-snapshots/data-source/sst-global-monthly-difference-average<br><br><br>This upload includes two additional files:<br>* SST - Global, Monthly Difference from Average _NOAA Climate.gov.pdf is a screenshot of the main Climate.gov site for these snapshots ()<br>* Cimate_gov_ Data Snapshots.pdf is a screenshot of the data download page for the full-resolution files. <br><br>
description: Data is divided in to folders by image resolution -- full size (zip), small (png) and large (png). Occasionally there may be one image missing in a particular size but available in another size.<br><br>Data downloaded from climate.gov 6/17/2025.