I view the work of Svensmark skeptically. I don't believe the GCR is that variant, i.e. its been relatively constant.
Now the GCR contribution does change according to the local solar activity. When the solar wind is strong, it interacts with the GCR more strongly, and when the solar wind in minimal, the GCR is relatively stronger. I think it more the case that clouds and earth's terrestrial weather is more strongly influenced by the sun's activity, but also by the chemical composition of the earth's atmosphere.
The big question these days is - are so-called greenhouse gases responsible for the apparent general warming of the earth's atmosphere during the last several decades? And if so, what must we do to mitigate the potentially negative effects?