For the few people who still need proof the planet is warming, NASA is complying today.
In a strongly worded release announcing 2012 was the ninth-warmest year on record on terra firma, NASA said one year doesn't mean much, but the the continuing warming of the planet is now a sure thing.
Scientists emphasize that weather patterns cause fluctuations in average temperatures from year to year, but the continued increase in greenhouse gas levels in the atmosphere assures that there will be a long-term rise in global temperatures. Each individual year will not necessarily be warmer than the previous year, but scientists expect each decade to be warmer than the previous decade.
"One more year of numbers isn't in itself significant," GISS climatologist Gavin Schmidt said. "What matters is this decade is warmer than the last decade, and that decade was warmer than the decade before. The planet is warming. The reason it's warming is because we are pumping increasing amounts of carbon dioxide into the atmosphere."
I can't find my source (which I think was NASA) but I once read that the Earth *has* had warming trends like this before but that they always occurred when the Earth was also closer to the sun. This time, the Earth *isn't* closer. So it has to be some other reason.
The IPCC's Temperature Dataset shows global cooling over the last 15 years.
The UK's HadCRUT3 dataset, considered the best, confirms the disappearance of global warming replaced by a slight cooling trend.
Here's a bunch of source data sets: http://www.c3headlines.com/datasets-temperature-climate.html
The Earth's climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era — and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives.
The current warming trend is of particular significance because most of it is very likely human-induced and proceeding at a rate that is unprecedented in the past 1,300 years.
This site also has a great graph that shows the amount of CO2 in the atmosphere for the past 650,000 years - it goes up and down but has recently shot up and it way higher than it ever has been in the last 650,000 years.
@Lars - No real cooling trend evident. I suppose if you cherry pick the data, you can say that after 2005 (the warmest in the CRUT3 data) the following years were cooler.
I see it differently. Since 2002, the annual global temperatures according to CRUT3 have been higher than any previous year. That's a decade long heat wave.
UK Met Office did not post the average global temperature for 2012 yet but reduced its future projections. NASA posted 2012 temperature but increases the temperature for many months and years in past, e.g., for 2011.
GISS in °C for 2011 as posted in 2013:
Jan 12 14.54 vs Jan 15 14.54
Here are data for fist 10 mo of 2012 after the decimal point:
32 37 45 55 67 56 46 58 61 69
36 39 49 60 70 59 51 57 66 70
So increase of past temperature was not uniform.
Can anybody explain this?