Excerpts from the Nobel Prize speech of former Vice President Al Gore

Seven years ago tomorrow, I read my own political obituary in a judgment that seemed to me harsh and mistaken — if not premature. But that unwelcome verdict also brought a precious if painful gift: an opportunity to search for fresh new ways to serve my purpose.

Unexpectedly, that quest has brought me here. Even though I fear my words cannot match this moment, I pray what I am feeling in my heart will be communicated clearly enough that those who hear me will say, "We must act."

We, the human species, are confronting a planetary emergency — a threat to the survival of our civilization that is gathering ominous and destructive potential even as we gather here. But there is hopeful news as well: we have the ability to solve this crisis and avoid the worst — though not all — of its consequences, if we act boldly, decisively and quickly.

However, despite a growing number of honorable exceptions, too many of the world's leaders are still best described in the words Winston Churchill applied to those who ignored Adolf Hitler's threat: "They go on in strange paradox, decided only to be undecided, resolved to be irresolute, adamant for drift, solid for fluidity, all powerful to be impotent.

In the last few months, it has been harder and harder to misinterpret the signs that our world is spinning out of kilter. Major cities in North and South America, Asia and Australia are nearly out of water due to massive droughts and melting glaciers. Desperate farmers are losing their livelihoods. Peoples in the frozen Arctic and on low-lying Pacific islands are planning evacuations of places they have long called home. Unprecedented wildfires have forced a half-million people from their homes in one country and caused a national emergency that almost brought down the government in another.

Indeed, without realizing it, we have begun to wage war on the earth itself. Now, we and the earth's climate are locked in a relationship familiar to war planners: "Mutually assured destruction."