The earths climate has always been subject to fluctuations due to a range of naturally occurring factors. But it has become increasingly evident that mankinds activities also contribute to climatic fluctuations. This dates back to the time when organised agriculture first began but has been greatly intensified over the past two centuries as industrialisation has led to significantly increased levels of carbon emissions.
The scientific evidence on climate change and mankinds role in contributing to it is overwhelming and impossible to ignore. But predicting how climate change will evolve and what consequences it will have remains extremely difficult. At a global level the picture is relatively clear but there is still insufficient understanding of how exactly climate change will affect specific regions and countries. Climate change cannot be understood properly if considered in isolation. Other important factors must be taken into account in particular, population growth. Climate change that may be manageable in a world with six billion people may not be controllable when the global population reaches nine billion as the United Nations estimates may be the case by 2051.
There are two main sources of uncertainty when it comes to predicting the speed and scale of climate change. The first is the future rate of man-made greenhouse gas emissions; will international efforts to mitigate emissions be effective, or will emerging economies go on growing well above historical rates and continue to generate most of their energy by burning dirty coal? The second is scientific uncertainty about the sensitivity of the climate system to additional man-made carbon dioxide emissions produced by the burning of fossil fuels; does doubling the amount in the atmosphere raise the average global temperature by two, three or four °C?
These uncertainties explain why the Intergovernmental Panel on Climate Change (IPCC), in its latest report in 2007, predicted that the temperature rise by the year 2100 would range from 1.8°C to 6.4°C. The lower number would mean a slow and surprise-free rise in temperature that would cause only moderate disruption in human societies though even this scenario would involve more frequent extreme weather events and the possible submergence of low-lying island states; the higher number would result in most of the existing farmland on the planet turning into burning desert.
However, recent findings, notably the drastic shrinkage since 2005 of the summer sea ice in the Arctic, have led some scientists to conclude that the IPCC predictions may in fact be on the low side. Indeed, in February 2009, Professor Chris Field, one of the authors of the IPCC report, warned that temperatures are likely to rise beyond the levels predicted and that the future climate is beyond anything that we have considered seriously in climate policy. These comments were based on the emergence of new data about emissions from the industrialising world which had not been available when earlier IPCC assessments had been reached. This more pessimistic view was reinforced at the International Scientific Conference on Climate Change, which took place in Copenhagen in March 2009.
Moreover, while the IPCCs report acknowledges the potential importance of large positive feedbacks, which would greatly speed up the warming process, it does not include them in its predictions because their complexity makes it impossible to incorporate them in climate models.
I'm sure we do vary in distance but not much year to year. There are so many cycles and cycles within cycles I wouldn't be surprised if our orbit dips in and out a bit every XXXXXX years in addition to any eccentricities in our orbit. There's even a theory ice ages are currently (last million years) induced by an orbit that more or less aligns with the invariable plane of the solar system, ie roughly the plane of Jupiter's orbit where more dust and debris resides. Sure, if the S hemisphere is having summers closer to the sun they will be warmer than the N hemisphere's summer - but thats just one factor. 
which bodes well for a continued interglacial into the distant future. But the value can ~quadruple so that %7 can reach more than a 1/4th difference in insolation. Now thats some extreme seasonal weather 
