delete some data in text file

[xiao zhang]

Hi~ guys~ I have a text file like this:

Experiment 01-14-97-2b9c
No. of Data Rows: 247
Temperature Pressure Relative Humidity
20.43 0.1654 0.243
16.48 0.2398 0.254
17.21 0.3985 0.265
18.40 0.1852 0.236
21.39 0.2998 0.293

And I have read in all the data. And what I want to do is to delete
same of the data if the the variation of temp is less than 1 K. And
then write them to another file. Do u have any good ideas to do that?
Thanks