Climate change threatens life as we know it. It is not only the focus of major scientific research agencies, but also governments and the private sector. Climate change can affect our lives in drastic ways and has been a topic of interest to the scientific community for longer than you might realize.
One of the most obvious indicators that Earth's climate changes was discovered not by any modern scientist, but by the forefathers of science who first looked to the stars - Kepler, Copernicus and Newton - and realized that Earth's position in space is not fixed. Their theories have since been consolidated and have incorporated climate data in what is now known as the Milankovitch Theory. This theory stipulates that changes in Earth's elliptical orbit around the sun (eccentricity), changes in the direction in which our axis points (precession) and changes in the tilt of the earth itself (obliquity) -- known as Milankovitch Cycles -- should contribute to changes in climate because of the different amounts of solar insolation received during these changes. Note: This theory does not question whether these three changes are occurring (it assumes they are). It postulates a link between the Milankovitch Cycles and climatic changes on Earth.
In order to know that the climate is changing, or has changed, it is important to provide a comparison. For example, the climate we observe today could be compared to that of the 1800's or over a longer time span such as several million years ago. The problem is that humans weren't collecting climate data during these time periods and obviously weren't present for most of the prehistoric past. Therefore scientists look to what's called paleo proxy data to evaluate changes in climate based on what we know about the time periods and on fossil evidence.
By analyzing these proxies, concentrations of atmospheric CO2, oceanic CO2, forest fires, aridity, measurements of sea level and more can be deciphered. These findings can then be compared to instrumental data about temperature, CO2, solar insolation, sea level, etc. This is the heart of climate science: understanding today's climate via instrumental observations and comparing it to the past via proxy data to show how climate has changed over time. The results show that Milankovitch Cycles have dominated the course of Earth's climate over the last several hundred million years, but there have been numerous instances of abrupt climate change that require more in-depth explanations and may serve as warnings for us today.
It should be noted that the greenhouse effect is very important for keeping earth warm in general. Without the greenhouse effect life wouldn't be possible today because the average temperature would be -18 degrees C. This implies that gasses like methane (CH4) and carbon dioxide (CO2) are inherently important in keeping the earth's temperature at hospitable levels.
So what does it mean that today's instrumental records show that CO2 concentrations in the atmosphere are rising, not only to levels not seen for several million years, but at a faster pace as well? It's a very big problem because the rate of the changes makes modeling the response of the planet to such increases very difficult. Factors like sea level change are hard to predict. For example different models predict anywhere from one meter to five meters of sea level rise -- a difference of 13 feet -- over the next century, complicating coastal planning and jeopardizing lives and property. Additionally, even though levels of atmospheric CO2 haven't reached the peak high of the prehistoric past, the rapidity of today's increases may affect climate and temperature in ways we cannot predict. Furthermore today's atmospheric CO2 levels, although not at the prehistoric peak, already correspond to a time period that was much warmer than today. Just a few degrees can mean large changes in global weather patterns and subsequently the global climate.
Climate change is already occurring. Some of this change has been linked to the interglacial cycle that we are exiting, according the Milankovitch Theory of prior glacial patterns. However, most of today's observed changes are occurring as a result of anthropogenic warming due to the large amount of CO2 that humans have added to the atmosphere. The increasing size of the Sahara Desert, reduced arctic sea ice formation in winter and summer, desertification of temperate lands, droughts and more frequent extreme weather events have all been linked to anthropogenic climate change.
Additionally, while sea level rises thus far have been small enough not to force global mass migrations, additional increases over this century will go well beyond the threshold for most coastal cities and population centers. Some places have already been flooded. Parts of the energy grid are already failing to meet reserve power levels for the hottest days in summer, according to the EIA. Furthermore, as drought conditions plague much of the US, cities are being forced to choose between electricity generation and crop irrigation as freshwater sources dwindle. Lastly, the battle between agricultural needs for freshwater and human consumption are becoming more and more strained as water sources start to dwindle, and agricultural pollution threatens those sources that remain.
These are just a few of the problems we will increasingly face. Climate change is very real and should be taken into account when deciding the future of our food, water and energy nexus.