Yes, The Climate is Changing

I was chatting with some friends yesterday while our families were enjoying a Saturday morning at one of our local parks. The topic of climate change came up and one of my friends commented that she is concerned about the changes and she doesn't like the pollution humans are generating but she doesn't know if human activity is the primary cause of climate change. This is one of my friends who I deeply trust and respect, someone I really look up to, so her comment made me think. I would have said - yes, I believe human activity is the primary cause of climate change. But why do I think that? Well, I realized that I didn't have a good reason. The truth is I think it because other people have told me so. I don't know what the science is behind that statement. And while I am a person of faith, I don't think it's a good idea to approach scientific claims as a matter of faith. I should take a look at the data before I decide what I believe.

So I went looking for data on climate change. I started with a few key questions. The first question is "Is climate change a reality?" The second question is "If climate change is a reality, is human activity the primary cause?" The third question is "If climate change is a reality, and if human activity is a primary cause, is it something to be concerned about?"

The answer to the first question appears to be a pretty clear yes, based on information I found on the websites from climate.nasa.gov (from NASA), http://www.climate.gov (from NOAA - the National Oceanic and Aeronautic Administration) and from the Intergovernmental Panel on Climate Change (IPCC) report (http://www.climatechange2013.org/images/report/WG1AR5_SPM_FINAL.pdf). If you want to look for yourself the NASA site is easier to read and has the best graphics, particularly on their key indicators page. The NOAA site offered some of the best articles and the IPCC report is the most detailed and their site also gives detailed information about the process they used to draw their conclusions. If you don't trust NASA, NOAA and the IPCC to report data accurately then this blog post won't mean much to you. We would need to have a different conversation altogether I suspect.

To sum up what I read, the climate is not only changing, it is changing rapidly. The last three decades have been the warmest on record over the past 1400 years.

Public Domain image. Source: climate.nasa.gov/key_indicators/

One of the counter-arguments that I read in several places is that global warming can't be true because the global temperature hasn't increased over the past ten years or so. This is true and the graph I posted shows it; over the past decade the global surface temperature has been stable. However, when I went looking for an explanation, there is a pretty simple one that is still consistent with climate change. This pause in the warming trend is attributed to both a decrease in solar output in the 2000's and due to the short term climate cycles of La Niña and the Pacific Decadal Oscillation over the past decade that have mixed surface ocean water into deeper ocean water. That sinks the heat deep in the ocean but the heat is still present, it's just not on the surface where it's being measured. Measurements of deep ocean temperature during this period show warming.

Public Domain image. Source: http://www.climate.gov/news-features/climate-qa/why-did-earth%E2%80%99s-surface-temperature-stop-rising-past-decade

During the same decade the polar ice has continued to melt. Arctic ice has decreased from over 6 million square kilometers in 2000 to under 4 million square kilometers in 2012. The Antarctic continent has lost 100 cubic kilometers of ice per year since 2002. This is just my thought, so it may be wrong or a bad analogy, but it seems to me that losing ice may be a better measure of warming than surface temperature. After all, if I set out a glass of ice water outside on a hot day the temperature of the water and the air immediately above it will remain steady until the ice melts. It's only after the ice melts that my drink becomes tepid.

Public Domain Image. Source: climate.nasa.gov/key_indicators/

Public Domain Image. Source: climate.nasa.goc/key_indicators/

So, looking at the data, my conclusion is that yes, the climate is changing. The earth is becoming warmer overall and it is happening rapidly. Which leads to my next question. Is human activity the primary cause of climate change today?