Carbon emissions have a severe, negative impact on the ecosystems our planet depends on. Everyone knows that carbon levels are higher than they were in the past, but the numbers are shocking: the EPA reports that since 1972, CO2 emissions have increased by 90% globally. NASA warns that this is nowhere near the end of this upward trend if we continue to burn fossil fuels and lead unsustainable lifestyles and business practices. NASA's calculations show that prior to 1950, CO2 levels had never reached more than 300 ppm (parts per million) in human history. However, today's levels have surpassed 400 ppm. If fossil fuel burning continues long term, NASA estimates CO2 will reach 1500 ppm within a few centuries. Inside Climate News sums up the potential disasters:

"Models have since shown this trend will kill forests and coral reefs, melt ice sheets and glaciers, turn fertile farm lands into deserts and swamp densely populated coastal areas with rising sea levels by the end of the century."

We have already begun to feel the impact of some consequences of rising CO2, with NOAA reporting that every year since 1976 has been warmer than average, sea levels have been rising, and coral reefs have been experiencing widespread bleaching. This is why many environmentalists and scientists are looking to more sustainable energy options to power our world.

New Energy Solutions

With all the grim news surrounding climate change and carbon emissions, renewable energy is on almost everyone's radar. However, despite the changes in global temperatures and the need to reduce emissions of greenhouse gases, many people see the switch to all sustainable fuel as improbable in the near future. While there is still a long way to go, the Union of Concerned Scientists estimates that by 2050, renewable energy will supply 80% of US power needs, drastically reducing the country's contribution of CO2 emissions.

The good news is that investments in renewable energy are picking up, and more people are interested in supporting sustainable initiatives. The Scientific American reports that investments rose from $9 billion in 2004 to $50 billion in 2015. Renewable energy is gaining momentum, and it could help power the cities of the future. What types of energy will we be using in the next few decades?

Types of Renewable Energies

When most people think of renewable energy, solar and wind power are typically the first sources to come to mind. However, there are many more resources being used and developed that are actually more common than these traditional sustainable energy sources. So which renewables will we see powering cities in the next few decades? According to Ohio University, these are the most common renewable resources gaining traction throughout the United States:

1. Hydropower (28%)

2. Biomass Wood (23%)

3. Biomass Biofuel (22%

4. Wind (17%)

5. Biomass Waste (5%)

6. Solar (3%)

7. Geothermal (2%)

These power sources are a major part of the solution to rising emissions, and will continue to help provide energy for many Americans. However, scientists continue to develop new technology to make renewable energy even more clean and efficient than it already is.

Developing New Clean Energy Sources

There are some very exciting new developments in the works for renewable energy. So what are some of the energy sources new technology will utilize for our cities of the future?

Nuclear Power

Nuclear fusion is used as an energy source as well as for weapon development, and companies like Lockheed Martin are working on sustainable solutions for fusion, such as onboard vehicle reactors, which would give commercial and military vehicles ongoing energy to power them wherever they go.

E. Coli Fuel

E. coli may be a dangerous food-borne bacteria, but scientists are harnessing its power to create sustainable propane fuel. The strain of e. coli used is harmless, so there's no concern that this fuel would put users at risk.

Better Batteries

Lithium ion batteries, the type used in today's electric vehicles, have several limitations, including slow charging, the use of non-recyclable materials, and loss of charge over time. Power Japan Plus is developing the Ryden Dual Carbon Battery which solves these problems by using all recyclable materials in its design, charging 20 times faster than lithium ion batteries, and the ability to be recharged many times without losing any energy capacity.

Hope for the Future

Aside from reducing our dependence on fossil fuels, powering our cities with renewable energy has other major benefits. It's ultimately affordable, better for public health and can add much-needed jobs to the economy. Water cooling, a necessary component of producing fossil fuels, is not needed for most other energy sources, so renewable energy can help reduce water use as well—extremely important as some states face droughts.

If this dream is to become reality, however, Americans will need to push for policies that improve infrastructure and support the switch to renewable energy sources. Reports show that only 9.5% of energy used in the United States in 2013 was sustainable. The country is responsible for 18% of the world's energy production, and it's time to do better. Our future cities can be sustainable!