Nobody denies that there was climate change in the past. But there were very different causes in all of those; some of those being random events, like changes in the earth's orbit or axis. But we also know that this time around, we humans are largely causing it, and it is very rapid, relatively speaking - by burning fossil fuels and adding carbon dioxide and other greenhouse gases to the atmosphere.
When sunspot activity goes up (every 11 years) then the suns irradiance goes up slightly:
Solar Radiation and Climate Experiment (SORCE) Fact Sheet : Feature Articles
Natural factors: Variations in the Sun
Solar variation - Wikipedia, the free encyclopedia
Climate myths: Global warming is down to the Sun, not humans - environment - 16 May 2007 - New Scientist
Does global warming mean that winter won't be cold? No, it does not. The climate is long term trends, and overall averages.