摘要：The Earth is warming on average, and most of the global warming of the past half-century
can very likely be attributed to human influence. But the climate in particular locations is
much more variable, raising the question of where and when local changes could become
perceptible enough to be obvious to people in the form of local warming that exceeds
interannual variability; indeed only a few studies have addressed the significance of local
signals relative to variability. It is well known that the largest total warming is expected to
occur in high latitudes, but high latitudes are also subject to the largest variability,
delaying the emergence of significant changes there. Here we show that due to the
small temperature variability from one year to another, the earliest emergence
of significant warming occurs in the summer season in low latitude countries (≈25°S–25°N). We also show that a local warming signal that exceeds past variability
is emerging at present, or will likely emerge in the next two decades, in many
tropical countries. Further, for most countries worldwide, a mean global warming of
1 °C is
sufficient for a significant temperature change, which is less than the total warming projected for any
economically plausible emission scenario. The most strongly affected countries emit small amounts
of CO2 per capita and have therefore contributed little to the changes in climate that they are
beginning to experience.
