If it was better than, why not now?

Question

If it was better for humanity during Medieval Warming Period that it warmed, why is it suddenly perceived as bad that we now have another warming trend? Why is it seen as unnatural that a warming trend is here, when the temperature changed "naturally" during the Little Ice Age and Medieval Warming Period? How can we be certain the change is unnatural now?

Answer 1

Warming is good for us as well.  We require less energy to heat our homes, so we have more disposable income.  I believe the current recession is due to the record cold driving up the price of energy, while people have to buy more instead of other items they may need, like paying the mortgage.

The change is natural now as well.  Over the last 100 years, man added at most 100ppm (parts per million) of co2 into the atmosphere.  That's just one molecule of co2 for every 1 million molecules of other gases.  How that that be harmful to the planet?

Answer 2

Scientific fact

Answer 3

Who said it was better for humanity during the MWP?  There were serious droughts (especially in the US SW) during that period.

Sometimes forest fires are started by lightening, sometimes they are started by careless human activity.  There is no reason consider previous natural climate changes as evidence that human activity isn't responsible for the current one.  Anything (volcano, asteroid, human SUV's) that significantly raises the level of atmospheric CO2 will cause a forcing on the planet resulting in some level of increased average global temperatures.  Since major volcano eruptions, orbital changes, solar irradiance, and every other known climate forcing has been determined to cause no more than 10 - 30% of our recent warming and since laboratory experiments prove that green-house gases actually do retain heat energy, it's a simple logical step to conclude that AGW is real.

Edit:

Jello - that's the equivalent of saying a match is only a very small fraction of the wood in a forest.  How can it possible cause any damage?  The concern over green house gas effect isn't based on the number of total molecules in the atmosphere, but on the percentage increase of those molecules that actually have a warming effect.  And CO2 is responsible for about 75% of the greenhouse warming, so a +30% increase in that effect is significant.

Answer 4

There is no evidence whatsoever to support the notion that human activity has any influence on the Global Climate.

Whether the planet is warming or cooling at the current moment is also debateable.

Answer 5

"If it was better for humanity during Medieval Warming Period"

Whoa whoa, that's a really huge "if".  There were extensive droughts during the MWP, so much so that they've even been termed "megadroughts".

"There is evidence for widespread hydrological anomalies from 900 to 1300 A.D. Prolonged droughts affected many parts of the western United States (especially eastern California and the western Great Basin) (14). Other parts of the world also experienced persistent hydrological anomalies (15)."

"A repetition of such anomalies today, with more than 10 times as many people on Earth as in High Medieval time, could be catastrophic."

http://www.geo.umass.edu/faculty/bradley...

"Why is it seen as unnatural that a warming trend is here, when the temperature changed "naturally" during the Little Ice Age and Medieval Warming Period?"

The temperature has changed naturally many times in the past.  But we have a pretty good idea what caused those changes - variations in the Earth's orbit and solar output, amplified by feedbacks like CO2.  These factors are not causing the current warming.

Over the past 30 years, all solar effects on the global climate have been in the direction of (slight) cooling, not warming.  This is during a very rapid period of global warming.

http://news.bbc.co.uk/2/hi/uk_news/62902...

http://www.pubs.royalsoc.ac.uk/media/pro...

If that’s not enough to convince you the Sun isn’t responsible, consider the fact that no scientific study has ever attributed more than one-third of the warming over the past 30 years to the Sun, and most attribute just 0-10% to the Sun.

http://answers.yahoo.com/question/index;...

"An often-cited 1980 study by Imbrie and Imbrie determined that 'Ignoring anthropogenic and other possible sources of variation acting at frequencies higher than one cycle per 19,000 years, this model predicts that the long-term cooling trend which began some 6,000 years ago will continue for the next 23,000 years.'"

http://en.wikipedia.org/wiki/Milankovitc...

http://www.sciencemag.org/cgi/content/ab...

So it's definitely not the Earth's orbital (Milankovitch) cycles either.

There are many basic scientific facts which can only be explained if the current global warming is being caused by an increased greenhouse effect due to carbon dioxide accumulating in the atmosphere from humans burning fossil fuels.

For example, the planet is warming as much or more during the night than day.  If the warming were due to the Sun, the planet should warm a lot more during the day when the Sun has influence.  Greenhouse gases trap heat all the time, so they warm the planet regardless of time of day.  Another example is that the upper atmosphere is cooling because the greenhouse gases trap the heat in the lower atmosphere.  If warming were due to the Sun, it would be warming all layers of the atmosphere.

http://answers.yahoo.com/question/index;...

Answer 6

During medieval times, we had no huge cities built on the shore, only a little above sea level. Can you say "Kat-ri-na", boys and girls?