The scientific community investigated it and issued a report saying that the effect of humans on the climate was discernable. That signaled the fact that we have grown large enough to alter the planet around us. Since 1995 the journals Science and Nature have regularly carried studies outlining our predicament. 1998 was the warmest year ever. Last week a study of the Himalayan ice core showed that the climate is warming.
Warm air produces more severe climactic events.
Warm air holds more water vapor so we have both more drought and more flood. There is a discernable rise in sea level. That might not seem like much, but small changes can produce enormous consequences in a crowded world. In Bangla Desh people can't feed themselves if ocean water rises enough to block the outflow of rivers, as happened two years ago. We can expect it to happen more frequently in the years ahead.