TWO KEY POINTS THAT NEED TO BE STRESSED IN A DISCUSSION OF CLIMATE CHANGE

 The first is that climate is not the same thing as weather. It is quite wrong to say that the climate has changed because we have had two or three hot dry summers. Those are simply weather. Climate change requires there to be an increase in the number of hot dry summers over a thirty year period, when compared to a previous thirty year period.

The second is that even if there has been a change as described above, we cannot simply say that the whole of that change is due to an increase in the concentration of CO2 in the atmosphere. There is good evidence that warming may also be caused by a change in cloud cover. Or changes in the circulation of the ocean currents. There is still a lot of argument about what proportion of warming can be attributed to each component. 

To argue these points is not unreasonable. It is unreasonable not to accept them. You cannot be a climate change denier if you accept that climate can and does change. The evidence must be based on sound statistics.