Negative/Pos Weights in Principal Components Factor Analysis

[homayoon]

Hi,

I intend to construct a mixed demographic and geography index from several sub indexes. (I.E population, land, agriculture land, CO2 emission, fuel energy, Nuclear Energy, urban and ...)
First, I deducted my sub indexes from 15 indexes to 7 indexes by using KMO test. Afterwards I used Principle Component Factor Analysis in order to select weights for these remained sub indexes. Now my problem is that 2 indexes named CO2 emission and urban have positive values in each Factor so they assign the positive weights in my demographic and geography index and based on these results, the more a country has CO2 emission, the high place it can reach in the mixed index.
So my question is, should I use these positive weights for the variables which have negative effect on the mixed index in real or I should change the weights to negative in some manner?

Thanks for your attention