So we're having unseasonably cool weather here in Chicago. Downright cold if you consider having temps in the 40's a few days before June. And over lunch I heard the whole, "How can we be having global warming if it's getting colder here and in other places as well?"
Well, climate is complex and there's no easy answer to that.
Global climate is a chaotic system that is currently in a temporary stable localized homeostasis. Certain factors influence the climate in well known ways -- for example, the length of days corresponding to temperature and seasons. The climatic system as a whole in general terms system usually bounces between fairly well established norms, displaying a partially predictable hysteresis response to influences.
The vast number of inputs and varying responses make predicting detailed climate response to specific events impossible. This is why we can predict winter and summer in advance (the seasons in general terms) but we have close to zero ability to accurately predict if it's going to rain the second tuesday of next month.
The reason most educated people are at least concerned about "Global Warming" is that nearly all locally stable chaotic systems have what is known as a "tipping point". You push them a little and they will come back to "center" with some minor random variations in between -- taking a partially unpredictable path trending back towards a predictable destination. However, if you push them past the "tipping point" -- all bets are off -- the system can fly off in any direction and run away chaotically or it could just as easily come back to rest in the same localized homeostasis or it may find a new stable locale.
That's why a little carbon emission might predictably cause a corresponding global warming but a lot of carbon emission might cause everything from an ice age to a long dry period of sprawling hot deserts -- or it might not cause any problems at all. One can honestly say that the best educated guess is we have no idea at all what will happen -- However, we can state at the same time that lots of carbon emissions are *MORE LIKELY* to push us into either an age of Deserts / Ice (something other than our current localized stable state) and the fact is that research or computer simulations can show both of those happening depending how they try to represent the climate system.
We can never hope to fully understand a truly chaotic system since by definition, it is random in response to certain inputs and beyond our complete understanding. However, we can understand issues like the "tipping point" and smaller effects on the system and try to avoid doing anything genuinely catastrophic. Reducing carbon emissions and anything else that is possible of influencing the climate is more likely to keep us in the stable locale we currently occupy (i.e. a habitable planet) not to mention that lessened dependence on fossil fuels has plenty of other economic and political benefits that are much better understood so we should pursue them anyhow.