There were a couple small problems in your code. First, there are 8 header lines, and the appropriate delimiter may be '\n'.
This works:
fid1 = fopen('GlobalTemp_v2.dat'); % have 20 columns
data1 = textscan(fid1, repmat('%f ', 1, 20), 'HeaderLines',8, 'Delimiter','\n');
Date = data1{1}; % Date (Calendar Years)
Temp = data1{14}; % Temperature
figure(1)
plot(Date, Temp)
grid
xlabel('Year')
ylabel('T (°F)')
The plot is just for fun for me, since I wanted to see what the data look like:
