Mayor Villaraigosa, UCLA Release Groundbreaking Climate Forecast for LA Region

Previous global climate models have proven too coarse for Los Angeles City and regional planners with 100-200 kilometer resolutions. The new UCLA study forecasts temperature changes from 2041 to 2060 down to a two kilometer resolution. With forecasting focused down to the neighborhood level, City and regional planners can begin preparing for Los Angeles' climate future.

Here is more info pulled from the C-Change.LA website:

“Mid-Century Warming in the Los Angeles Region” is the first study to provide specific climate-change predictions for the greater Los Angeles area, with unique predictions down to the neighborhood level.

This temperature study is the first of the five part series of releases coming from the Climate Change in the Los Angeles Region project. Providing a range of climate impacts that cover the best and worst case emissions scenarios for the Los Angeles region by the coming midcentury, it shows that even the best case scenario will lead to significant warming due to emissions that are already moving through the Earth’s atmosphere.

The report, the most sophisticated regional climate study ever developed, was produced by UCLA with funding and support from the city of Los Angeles (news release), in partnership with the Los Angeles Regional Collaborative for Climate Action and Sustainability (LARC).

Results

This groundbreaking new study shows that climate change will cause temperatures in the Los Angeles region to rise by an average of 4-5°F by the middle of this century, tripling the number of extremely hot days in the downtown area and quadrupling the number in the valleys and at high elevations.

The study looked at the years 2041–60 to predict the average temperature change by mid-century. There may be highs or lows across that time but on average the Los Angeles region will be warmer.

All areas across the Los Angeles region will experience warming in the coming midcentury. Los Angeles will begin to observe a gradual rise in annual average temperatures over the next 30 years.

The actual amount of temperature increase shows in degrees of warming. And there are several ways to look at these averages that exist across the twenty-year period.

An important aspect of this study is that it shows where different areas will experience different degrees of warming.

According to the study, coastal areas like Santa Monica and Long Beach are likely to warm an average of 3 to 4 degrees. Dense urban areas like downtown Los Angeles and the San Fernando and San Gabriel valleys will warm an average of 4 degrees, and mountain and desert regions like Palm Springs and Lancaster will warm 4 to 5 degrees.

When we think of temperatures, we tend to think of our sensory experience of weather. The degrees of warming observed in this study have a very different meaning than morning temperatures versus afternoon temperatures that we may experience in a single day. The average rise in temperatures across not only a year but two decades, means that the climate itself has shifted.

Southern Californians should expect slightly warmer winters and springs but much warmer summers and falls, with more frequent heat waves.

Number of Hot Days

The number of days when the temperature will climb above 95 degrees will increase two to four times, depending on the location. Temperatures now seen only on the seven hottest days of the year in each region will occur two to six times as often.

This study zooms in so close that it is able to observe global climate influences on the level of the neighborhood. We now know the likelihood of how many fo these hot days to expect in each of our neighborhoods.

Coast, Inland, Mountains

Warming over the ocean and coastal areas is slower due to the high heat capacity of water, meaning that water can actually absorb a lot of energy without changing temperature very much. Think of a bathtub filled with cool water. Now, in the bathroom where that bathtub sits, imagine there is warm air in the room. The water in the tub will not become warm due to the warm air in the room, it could, but it would take a very very long time. It is the temperature of the air in the room that will be changed by presence of cool water. The air would actually begin to cool. In other words, it takes much longer for air temperatures to affect water temperatures than the other way around.

It is not only the temperature influence of a cool body of water that can cool the air, the very act of evaporation diminishes the likelihood of extreme high temperatures. This is why areas that already tend to be dry will warm faster and more intensely as the study reveals. Water has the ability to break, or buffer, the heat through evaporation, up to a point.

The mountain ranges, even small ones, act as a barrier to shared airflow from the coast. This is a likely contributor to the greater increases in hot days that are shown for areas on the inland side of Santa Monica Mountains, like Woodland Hills, where there is less opportunity for ocean influence. The San Fernando Valley will warm about 10% more than the L.A. Basin. Along this same track, areas show more warming the further they are away from the coast.

Mountains not only impact valleys and inland areas, they also experience degrees of increased average temperatures similar to desert areas. This does not mean that the mountains will be as hot as desert areas, it means that they will experience a similar amount of increase to their average.

The study shows that both mountains and deserts will experience an average warming of about 5°F. For example, today’s temperature at the top of the San Gabriel Mountains reads 70°F, by the year 2041, that same location, during a similar time of year, will be 75°F. Similarly, where today’s temperature in Bakersfield is 95°F, 30 years from now it will be 100°F.

The Range of Likely Outcomes

Global Climate Models are based on emissions scenarios. This study utilized information from the the best and worst-case-scenario for emissions. This allows the study to observe the full range of likely outcomes.  This is important because, even if the world has unanticipated — and perhaps unrealistic — success in drastically reducing greenhouse gas emissions, or best-case-scenario, the greater Los Angeles area will still warm to about 70 percent of the predicted levels of business-as-usual, or worst-case, scenario.

In other words, no matter what, significant warming will still occur by the approaching midcentury time period. This is because a certain amount of greenhouse gases are already ‘committed’ to the system.

However, by observing this range, the study enables us to have a clearer picture on the challenges to come.