# In the northern hemisphere only, what percentage of the surface is land?

Across the whole Earth, about 70% of the surface is water and 30% is land.

What I want, though, is to restrict the scope to the northern hemisphere (NH) only. What percentage of NH surface is land?

It would also be good to clarify exactly how we define "land". If I'm not mistaken, the 70/30 split of water/land actually places inland rivers and lakes as land area.

Please also cite a source for this. The only google result I found with an answer was yahoo questions.

• Good question! The best answer will give you a quantitative estimate, and show you how this was done in a GIS or programming language. I hope someone can give you this. Commented Sep 10, 2015 at 11:57

I get 40.4%

With a workflow using a tiny bit of Python.

1. After Polygorial‘s comment I am adding (Updated on Feb 17, 2021) point zero to state more explicitly that this method requires a map like the one I used (Gall-Peters projection) with equal area projection, as regions of same area on the Earth’s surface will have the same area on the map, and therefore same number of pixels.

2. Invert and import B/W image of equal area projection for the Northern hemisphere (land = white pixels). Source of original image (full globe): Wikimedia Commons.

3. Store as Numpy array.

4. Calculate total number of pixels in image array (black + white).

5. Calculate total number of white pixels (1s) by summing the entire array (black pixels (0s) will amount to zero).

6. Calculate percentage of white pixels.

UPDATE September 20, 2018

As suggested by @JeopardyTempest in a comment, as a validation test I run the script for the full image with both hemispheres, and got the expected 30%

• Love your answer, shows a simpler/ingenious way to solve it, and explains your work process, so very useful. It's of course a bit of a rough estimate depending upon the pixel resolution of the image... but for many purposes, that's plenty fine. Stack Exchange can always use more thoughtful answers like these. Thanks! Commented Sep 20, 2018 at 17:13
• (For good measure, happen to be easy to get the Southern Hemisphere number, since it sort of naturally goes with the question? [Plus serves as a further check in how close it is in methodology given the full-Earth values are pretty well publicized]) Commented Sep 20, 2018 at 20:20
• Thanks for your comment. Yes, the resolution of the image may limit the accuracy. I was hoping to get high resolution data like the Global Land One-km Base Elevation from the US National Geophysical Data Center (ngdc.noaa.gov/mgg/topo/gltiles.html), but it would have meant merging 8 huge arrays, threshold work, and then reproject. As you imply probably beyond the scope of a Stack Exchange answer. Also we might want to subtract the estimated rivers and streams coverage in @farrenthorpe 's answer. Commented Sep 20, 2018 at 22:34
• Always a fan of keep it simple, unless it's something really asking for intense precision :-) Commented Sep 20, 2018 at 23:09
• I run the code using the full globe and got the expected 30% land coverage. Updated answer with the details. Thanks for suggesting it. Commented Sep 21, 2018 at 3:30

The spatial distribution of ocean regions and continents is unevenly arranged across the Earth's surface. In the Northern Hemisphere, the ratio of land to ocean is about 1 to 1.5. The ratio of land to ocean in the Southern Hemisphere is 1 to 4. This greater abundance of ocean surface has some fascinating effects on the environment of the southern half of our planet. For example, climate of Southern Hemisphere locations is often more moderate when compared to similar places in the Northern Hemisphere. This fact is primarily due to the presence of large amounts of heat energy stored in the oceans.

This equates to a measurement of ~40% land in the northern hemisphere. This agrees with the northern hemisphere azimuthal equal-area map image below.

The surface area of the Earth covered by lakes and rivers is a fraction of a percent, so their classification does not really change the answer. However, you would get a slightly different answer if you consider land to be any continental crust (including seas not on ocean crust). If you define a year and a definition of "land" that you are satisfied with, an exact calculation could be made with GIS software.

Rivers and streams are likely to cover 0.30–0.56% of the land surface [of Earth]

• So close to a quantitative answer! I hope someone can follow up on your last sentence. Commented Sep 10, 2015 at 11:58
• Are you sure rivers and lakes make up only a tiny fraction? Rivers in particular can be very long and can branch all over the place. All those gullies might add up. Commented Sep 10, 2015 at 19:53