Merge pull request #24 from hannahzafar/foundations1_fix

Edited foundations1 (fix from error before)

notebooks/foundations/energy-balance-model.ipynb

@@ -244,7 +244,9 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    ":$  to bee populated"
+    "The surface albedo feedback, also known as the ice-albedo feedback, pertains primarily to the high latitudes, where snow and ice are present. Snow and ice have very high albedo (reflectivity). Snow has the highest albedo (up to 90%), while sea ice albedo ranges from 50-70%. Melt ponds further reduce the albedo, and as ice recedes, open ocean can be as low as 6%.\n",
+    "\n",
+    "This process consitutes a positive feedback loop: melt of snow and ice decreases albedo, causing additional radiation absorption. More absorption causes temperatures to rise, which further contributes to melt, restarting the cycle."
    ]
   },
   {
@@ -286,6 +288,31 @@
     "### 4. Cloud Feedback "
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The cloud feedback mechanism is the most complex feedback discussed in this tutorial. There are several reasons for this. Clouds interact with both shortwave (SW) solar radiation and longwave (LW) terrestrial radiation and exert varying radiative effects depending on their properties (cloud type, height, optical depth, liquid and ice water content, particule sizes, etc).\n",
+    "\n",
+    "Generally, high-level clouds do not interact much with solar radiation but easily absorb terrestrial radiation, preventing its loss to space and contribute to warming. Low-level clouds reflect solar radiation during the day, which contributes to cooling, but absorb some terrestrial radiation,  contributing to warming (particularly at night!). Thus, high-level clouds tend to exert a positive climate feedback, while low-level clouds tend to exert an overall negative climate feedback."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "![High cloud versus low cloud radiative effects](../images/2-whycloudsare.jpg)<br>\n",
+    "[Credit: Paulo Ceppi](https://phys.org/news/2020-09-clouds-piece-climate-puzzle.html)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Cloud feedbacks produced by climate models tend to vary greatly, which is largely attributed to the issue of scale in modern GCMs (ESMs??). GCMs are at resolutions much too large to resolve the microscopic processes dictating the formation and properties of clouds.\n",
+    "Cloud formation and lifetime is additionally complex as it is highly dependent on atmospheric aerosol loading, which is another complex discussion. Of course, clouds are also intrinsically tied to atmospheric water vapor content."
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},