Adjusting your driving style will have the biggest influence here. Try to be a little more aggressive with the car, without braking traction or excessively sliding the tyres.
If track and ambient temperatures are cold and you still can't get sufficient heat into the tyres, and assuming pressures are correct, do the following modifications one at a time (ordered from more to less influence):
Take care when trying to push the tyres when they are cold as it can lead to the tyres graining. This can rapidly decrease the amount of tyre grip (depending on the amount of graining occuring) and increase wear.
It is however possible to drive through the graining (providing the amount of graining is "slight") and bring the tyres back by being smooth and avoiding sliding the tyres.