hmm.....first a small change in average temp will bring on change in weather patterns , We will see most of the effects in the economy and health of the worlds population through famine in areas that are 3rd world so to speak. modern industrial nations will see big hit to the economy with disruption in crop production,,further increases in respiratory illness...If i was to sum up my thoughts the answer would be "slowly but innevitably" , ther are thoughts that the earth since it was formed that has undergone many warming periods followed by ice ages,,due to speculated factors such as development of plant life(which directly changes atmospheric gas %) or natural disasters of meteor,,,volcanic eruptions, tsunami,,,etc..
we can only measure what we are finding right now which is rising sea levels, and temperature monitoring of the atmosphere and sea water.